Patent Application
20230291493
The embodiments disclosed herein relate to optical data communication. Optical data communication systems operate by modulating laser light to encode digital data patterns. The modulated laser light is transmitted through an optical data network from a sending node to a receiving node. The modulated laser light having arrived at the receiving node is de-modulated to obtain the original digital data patterns. Therefore, implementation and operation of optical data communication systems is dependent upon having reliable and efficient laser light sources. Also, it is desirable for the laser light sources of optical data communication systems to have a minimal form factor and be designed as efficiently as possible with regard to expense and energy consumption. It is within this context that the present disclosed embodiments arise.
In an example embodiment, an optical distribution network is disclosed. The optical distribution network includes a fore-positioned optical multiplexer section that has a plurality of optical inputs and a plurality of intermediate optical outputs. Each of the plurality of optical inputs of the fore-positioned optical multiplexer section is configured to receive a respective one of a plurality of input light signals of different wavelengths. The fore-positioned optical multiplexer section is configured to multiplex a unique subset of the plurality of input light signals onto each of the plurality of intermediate optical outputs. The unique subset of the plurality of input light signals that is multiplexed on any given one of the plurality of intermediate optical outputs is mutually exclusive with respect to the plurality of input light signals that are multiplexed on others of the plurality of intermediate optical outputs. The optical distribution network also includes an optical coupler section that has a plurality of optical inputs respectively optically connected to the plurality of intermediate optical outputs of the fore-positioned optical multiplexer section. The optical coupler section has a plurality of optical outputs that correspond to a plurality of optical outputs of the optical distribution network. The optical coupler section is configured to distribute a portion of each light signal received at each of the plurality of optical inputs of the optical coupler section to each and every one of the plurality of optical outputs of the optical coupler section.
In an example embodiment, a laser module is disclosed. The laser module includes a laser array that includes a plurality of lasers. Each laser of the plurality of lasers is configured to generate and output a different one of a plurality of wavelengths of continuous wave laser light. The plurality of lasers are arranged in the laser array such that a sequence of the plurality of wavelengths of continuous wave laser light is non-monotonically ordered across the laser array. The laser module also includes an optical distribution network that includes a fore-positioned optical multiplexer section and an optical coupler section that is disposed after the fore-positioned optical multiplexer section with respect to a light propagation direction through the optical distribution network. The fore-positioned optical multiplexer section has a plurality of optical inputs that are optically connected to the plurality of lasers, such that the non-monotonic ordering of the sequence of the plurality of wavelengths of continuous wave laser light across the laser array matches an ordering of wavelength acceptance passbands of the plurality of optical inputs of the fore-positioned optical multiplexer section. The fore-positioned optical multiplexer section has a plurality of intermediate optical outputs. The fore-positioned optical multiplexer section is configured to multiplex a unique and mutually exclusive subset of the plurality of wavelengths of continuous wave laser light onto each of the plurality of intermediate optical outputs. The optical coupler section has a plurality of optical inputs respectively optically connected to the plurality of intermediate optical outputs of the fore-positioned optical multiplexer section. The optical coupler section has a plurality of optical outputs respectively corresponding to each of a plurality of optical outputs of the optical distribution network and a plurality of outputs of the laser module. The optical coupler section is configured to distribute a portion of each light signal received at each of the plurality of optical inputs of the optical coupler section to each and every one of the plurality of optical outputs of the optical coupler section.
A method is disclosed for operating a laser module. The method includes operating a plurality of lasers to respectively generate a plurality of input light signals of different wavelengths. The method also includes conveying the plurality of input light signals to a plurality of optical inputs of a fore-positioned optical multiplexer section, such that each of the plurality of optical inputs of the fore-positioned optical multiplexer section receives a respective one of the plurality of input light signals of different wavelengths. The method also includes operating the fore-positioned optical multiplexer section to multiplex a unique subset of the plurality of input light signals onto each of a plurality of intermediate optical outputs, such that the unique subset of the plurality of input light signals that is multiplexed on any given one of the plurality of intermediate optical outputs is mutually exclusive with respect to the plurality of input light signals that are multiplexed on others of the plurality of intermediate optical outputs. The method also includes conveying the unique subsets of the plurality of input light signals from the plurality of intermediate optical outputs to a plurality of optical inputs of an optical coupler section, such that a different unique subset of the plurality of input light signals is respectively conveyed to each of the plurality of optical inputs of an optical coupler section. The method also includes operating the optical coupler section to distribute a portion of each light signal that is received at each of the plurality of optical inputs of the optical coupler section to each and every one of a plurality of optical outputs of the optical coupler section.
In the following description, numerous specific details are set forth in order to provide an understanding of the embodiments disclosed herein. It will be apparent, however, to one skilled in the art that the embodiments disclosed herein may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail in order not to unnecessarily obscure the disclosed embodiments.
High bandwidth, multi-wavelength WDM (Wavelength-Division Multiplexing) systems are used to meet the needs of increasing interconnect bandwidth requirements. In some implementations of these WDM systems, a remote laser array that outputs multiple wavelengths of continuous wave (CW) laser light is combined with an optical distribution network to transmit optical power at multiple wavelengths across multiple optical output ports. In some embodiments, a number N of optical output ports is less than a number M of optical input ports at some point in the optical train, which necessitates implementation of optical multiplexer (MUX) functionality. In some embodiments, arrayed waveguide gratings or cascaded Mach-Zehnder interferometers are used to combine (multiplex) multiple (M) wavelengths of light into one optical channel, where this one optical channel is then combined with a 1×N optical splitter to realize an M×N optical distribution network. However, an M×1 optical MUX requires optical filtering with passbands that are bandwidth-limited by the light wavelength spacing, which can in turn result in undesired temperature sensitivity. Example embodiments are disclosed herein for an M optical input by N optical output (M×N) optical (light) distribution network (for N less than M) that uses a reduced number of optical MUX stages (as compared to an M×1 cascaded optical MUX network) in combination with a star coupler at the output. In comparison to using an M×1 optical MUX system followed by 1×N optical splitting, the M×N optical distribution network disclosed herein enables lower temperature sensitivity by allowing for wider optical MUX passbands.
Also, for a cascaded optical MUX network, the required sequence of input light wavelengths is typically not increasing or decreasing in order of the input channel. Rather, the sequence of input light wavelengths is a non-monotonic sequence that has to match the input light wavelength passbands of the first optical MUX stage. In various example embodiments disclosed herein, the light wavelength sequence on the laser array is configured to match the input light wavelength passbands of the first optical MUX stage to enable direct one-to-one coupling of the lasers in the laser array with the input channels of the optical distribution network without the need for any additional optical routing or crossings. It should be understood that the light wavelength sequence on the laser array is the order in which the different laser wavelengths occur from laser-to-adjacently positioned laser in a single direction across the laser array.
In some embodiments, each of the optical fibers 113-1 to 113-N of the N-port optical fiber array 113 is connected to route the multiple wavelengths (λ1 to λM) of CW laser light that it receives from the optical power supply 111 to a corresponding optical supply port 115-1 to 115-N on an electro-optical chip 102. In this manner, the N-port optical fiber array 113 delivers the M wavelengths (λ1 to λM) of CW laser light to each of N optical supply ports 115-1 to 115-N on the electro-optical chip 102. In some embodiments, the electro-optical chip 102 is a CMOS (Complementary Metal Oxide Semiconductor) and/or an SOI (silicon-on-insulator) photonic/electronic chip, that sends and receives data in an optical data communication system. In some embodiments, the electro-optical chip 102 is the TeraPHY™ chip produced by Ayar Labs, Inc., of Santa Clara, Calif., as described in U.S. patent application Ser. No. 17/184,537, which is incorporated herein by reference in its entirety for all purposes.
In some embodiments, for the M×N optical distribution network 103 where the number N of optical output ports 107-1 to 107-N is less than the number M of CW light output channels of the laser array 101, the M×N optical distribution network 103 includes at least one stage of optical wavelength multiplexers (MUX's). In some embodiments, optical wavelength multiplexing is implemented by using a series of cascaded Mach-Zehnder interferometers (MZIs), where each MZI is capable of combining two wavelengths of light incident on the two MZI input ports onto one of the MZI output ports. In some embodiments, a cascaded MZI system is used to realize M×1 multiplexing, where M=2n and n is an integer. In this type of cascaded MZI system, the final MZI stage of the cascaded MZI system has a free spectral range (FSR) approximately equal to the light wavelength spacing, where the MZI FSR is doubled in each preceding stage of the cascaded MZI system. In some embodiments, this type of cascaded MZI system is used to implement WDM in an optical data communication application. The MZI in the above-mentioned cascaded MZI system serves as a light wavelength MUX. However, in various embodiments, it is not necessary to use an MZI as the MUX in the M×N optical distribution network 103. For example, in some embodiments, instead of the using the MZI as the MUX device, the M×N optical distribution network 103 can be implemented using essentially any other type of optical MUX device, such as a ring-based add-drop filter, a grating-based add-drop filter, a directional coupler, and/or an integrated dichroic filter, among others, by way of example.
For the M×N optical distribution network 103 that implements a cascaded MUX network, the light wavelength sequence of the optical input ports 106-1 to 106-M may not be monotonically increasing or decreasing, and the light wavelength sequence of the optical input ports 106-1 to 106-M should be adjusted to match the acceptable light wavelength passbands of the MUX devices. For example, when using MZI's as the MUX's in the M×N optical distribution network 103, the first MZI stage has an FSR that is equal to the light wavelength spacing multiplied by M and a half-FSR shift in the transmission function of the two input ports of the first MZI stage. Therefore, the two light wavelengths entering the two input ports of each MZI are chosen such that the two light wavelengths are separated by the wavelength spacing multiplied by M/2. Therefore, to enable one-to-one coupling of each physical laser channel of the laser array 101 to the corresponding physical input channel (106-1 to 106-N) of the cascaded MUX network within the M×N optical distribution network 103, embodiments are disclosed herein for a modification of the optical power supply 111 in which the light wavelength sequence of the laser array 101 is configured to satisfy the input light wavelength passband sequence requirements of the cascaded MUX network within the M×N optical distribution network 103.
In order to directly use the above-described cascaded MUX network to implement the M×N optical distribution network 103, a 1×N optical power splitter is positioned after the M×1 MUX. One drawback of this approach is that the final MUX stage in the M×1 wavelength optical combiner requires an acceptance passband that is substantially narrower than the light wavelength spacing. Since the spectral response of any material with a non-zero thermo-optic coefficient will shift with temperature, a narrower light wavelength passband will lead to increased temperature sensitivity in the insertion loss of the M×N optical distribution network 103. For example, in an MZI-based 8×1 optical combiner, the final MZI should have an FSR that is approximately equal to the light wavelength spacing, which will result in a light wavelength passband that is substantially narrower than the light wavelength spacing. If the peaks of the light wavelength passbands of the MUX's (e.g., MZI's) in the first MUX (MZI) stage are nominally aligned with the input light wavelengths of the lasers, a shift in the peaks of the light wavelength passbands of the MUX's (e.g., MZI's) in the first MUX (MZI) stage due to a shift in the temperature will result in a decrease in the output optical power of the M×N optical distribution network 103.
Embodiments are disclosed herein for an M×N optical distribution network (with N less than M) in which the number of MUX stages is reduced as compared to a M×1 optical distribution network. Also, in various embodiments, the M×N optical distribution network disclosed herein includes an optical star coupler implemented to distribute light from a number of intermediate optical outputs of a reduced MUX front-end network to the N optical output ports of the M×N optical distribution network. In these embodiments, the reduced MUX front-end network refers to an M×O front-end network, where O is greater than 1, and where O is less than or equal to N (1<O≤N), and where each of the O output ports of the M×O front-end network conveys a unique set of light wavelengths. In these embodiments, an O×N star coupler is optically connected to the O output ports of the M×O front-end network to complete formation of the M×N optical distribution network, where each of the N optical outputs of the M×N optical distribution network conveys all M of the CW laser light input wavelengths. In comparison with the M×N optical distribution network implemented using the M×1 cascaded MUX network followed by the 1×N network, the M×N optical distribution network implemented using the M×O front-end network followed by the O×N star coupler provides for lower optical insertion loss because it is implemented using fewer functional stages, which corresponds to fewer optical components per pathway in order to realize M×N CW laser light distribution functionality. Also, in comparison with the M×N optical distribution network implemented using the M×1 cascaded MUX network followed by the 1×N network, the M×N optical distribution network implemented using the M×O front-end network followed by the O×N star coupler provides for decreased temperature sensitivity because the fore-positioned MUX stages have a broader FSR and can therefore support a broader CW laser light input wavelength passband. A broader CW laser light input wavelength passband will provide for lower optical insertion loss variation if the MUX spectrum shifts due to changes in temperature.
The MZI 203-1 has two optical inputs 203i1-1 and 203i2-1 that receive CW laser light input wavelengths λ6 and λ2, respectively. The two optical inputs 203i1-1 and 203i2-1 correspond to input channels 1 and 2 of the M×1 cascaded MUX network 200, respectively. The MZI 203-1 has an optical output 203o-1. The MZI 203-1 is configured to combine the two CW laser light input wavelengths λ6 and λ2 onto the one optical output 203o-1.
The MZI 203-2 has two optical inputs 203i1-2 and 203i2-2 that receive CW laser light input wavelengths λ4 and λ8, respectively. The two optical inputs 203i1-2 and 203i2-2 correspond to input channels 3 and 4 of the M×1 cascaded MUX network 200, respectively. The MZI 203-2 has an optical output 203o-2. The MZI 203-2 is configured to combine the two CW laser light input wavelengths λ4 and λ8 onto the one optical output 203o-2.
The MZI 203-3 has two optical inputs 203i1-3 and 203i2-3 that receive CW laser light input wavelengths λ1 and λ5, respectively. The two optical inputs 203i1-3 and 203i2-3 correspond to input channels 5 and 6 of the M×1 cascaded MUX network 200, respectively. The MZI 203-3 has an optical output 203o-3. The MZI 203-3 is configured to combine the two CW laser light input wavelengths λ1 and λ5 onto the one optical output 203o-3.
The MZI 203-4 has two optical inputs 203i1-4 and 203i2-4 that receive CW laser light input wavelengths λ3 and λ7, respectively. The two optical inputs 203i1-4 and 203i2-4 correspond to input channels 7 and 8 of the M×1 cascaded MUX network 200, respectively. The MZI 203-4 has an optical output 203o-4. The MZI 203-4 is configured to combine the two CW laser light input wavelengths λ3 and λ7 onto the one optical output 203o-4.
The MZI 205-1 has two optical inputs 205i1-1 and 205i2-1 optically connected to the optical outputs 203o-1 and 203o-2, respectively, of the MZI 203-1 and the MZI 203-2, respectively. In this manner, the CW laser light input wavelengths λ2 and λ6 are conveyed to the optical input 205i1-1, and the CW laser light input wavelengths λ4 and λ8 are conveyed to the optical input 205i2-1. The MZI 205-1 has an optical output 205o-1. The MZI 205-1 is configured to combine the four CW laser light input wavelengths λ2, λ4, λ6, and λ8 onto the one optical output 205o-1.
The MZI 205-2 has two optical inputs 205i1-2 and 205i2-2 optically connected to the optical outputs 203o-3 and 203o-4, respectively, of the MZI 203-3 and the MZI 203-4, respectively. In this manner, the CW laser light input wavelengths λ1 and λ5 are conveyed to the optical input 205i1-2, and the CW laser light input wavelengths λ3 and λ7 are conveyed to the optical input 205i2-2. The MZI 205-2 has an optical output 205o-2. The MZI 205-2 is configured to combine the four CW laser light input wavelengths λ1, λ3, λ5, and λ7 onto the one optical output 205o-2.
The MZI 207 has two optical inputs 207i1 and 207i2 optically connected to the optical outputs 205o-1 and 205o-2, respectively, of the MZI 205-1 and the MZI 205-2, respectively. In this manner, the CW laser light input wavelengths λ2, λ4, λ6, and λ8 are conveyed to the optical input 207i1, and the CW laser light input wavelengths λ1, λ3, λ5, and λ7 are conveyed to the optical input 207i2. The MZI 207 has an optical output 207o. The MZI 207 is configured to combine the eight CW laser light input wavelengths λ1, λ2, λ3, λ4, λ5, λ6, λ7, and λ8 onto the one optical output 207o.
The architecture of the M×1 cascaded MUX network 200 can be expanded by adding MZI stages at the front-end side (at the channel input side, i.e., left side), such that the number (M) of channel inputs equal 2n (i.e., M=2n) for arbitrary (n), where (n) is the integer number of MZI stages. In the 8×1 wavelength combiner example of
The optical path length difference in the MZI's in each consecutive MZI stage 201-1, 201-2, and 201-3 is approximately doubled to decrease the FSR by approximately two in each consecutive MZI stage. For example, the optical path length in a given one of the MZI's 205-1 and 205-2 in the second MZI stage 201-2 is approximately two times the optical path length in a given one of the MZI's 203-1, 203-2, 203-4, and 203-5 in the first MZI stage 201-1, such that the FSR in the second MZI stage 201-2 is approximately one-half of the FSR in the first MZI stage 201-1. Similarly, the optical path length in the MZI 207 in the third MZI stage 201-3 is approximately two times the optical path length in a given one of the MZI's 205-1 and 205-2 in the second MZI stage 201-2, such that the FSR in the third MZI stage 201-3 is approximately one-half of the FSR in the second MZI stage 201-2. The increase in the optical path length in the MZI's of successive MZI stages is shown in the MZI's 203-1, 203-2, 203-3, 203-4, 205-1, 205-2, and 207
In some embodiments, the M×1 (M=8) cascaded MUX network 200 is implemented as a multiplexer/demultiplexer (MUX/DEMUX) in a WDM system. In some embodiments, the output 207o of the M×1 cascaded MUX network 200 is optically connected to a 1×N optical splitter to create an M×N optical distribution network, where M is 8. In some embodiments, an M×1 cascaded MUX network of arbitrary M, where M=2n with (n) being an integer, similar to the M×1 cascaded MUX network 200, has an optical output optically connected to an optical input of a 1×N optical splitter to create an M×N optical distribution network.
Each of the MUX's 303-S-Y of the MUX stages 301-1 to 301-P is configured to receive a first set of one or more distinct wavelengths of CW laser light on a corresponding first optical input 303i1-S-Y and a second set of one or more distinct wavelengths of CW laser light on a corresponding second optical input 303i2-S-Y, where the first and second sets of one or more distinct wavelengths of CW laser light are mutually exclusive of each other. Also, each MUX 303-S-Y is configured to output a third set of multiple distinct wavelengths of CW laser light onto a corresponding common (single) optical output 303o-S-Y. The third set of multiple distinct wavelengths of CW laser light conveyed through the optical output 303o-S-Y includes each of the distinct wavelengths of CW laser light of the first and second sets of one or more distinct wavelengths of CW laser light that are received on the corresponding first optical input 303i1-S-Y and the corresponding second optical input 303i2-S-Y, respectively. The last MUX stage 301-P of the fore-positioned optical MUX section 313 includes a number O of MUX's 303-P-1 to 303-P-O, where O is an integer equal to (M/2P), i.e., O=(M/2P), where M is the number optical input channels, and P is the number of optical MUX stages in the fore-positioned optical MUX section 313. Therefore, the MUX's 303-P-1 to 303-P-O of the last MUX stage 301-P of the fore-positioned optical MUX section 313 collectively have the number O of optical outputs 305-1 to 305-O. The O optical outputs 305-1 to 305-O of the fore-positioned optical MUX section 313 are referred to as O intermediate optical output ports of the M×N optical distribution network 300.
The O optical outputs 305-1 to 305-O are optically connected to O optical inputs 309-1 to 309-O, respectively, of an O×N star coupler 307 within the optical coupler section 315 that follows the fore-positioned optical MUX section 313 within the M×N optical distribution network 300. Each of the O optical outputs 305-1 to 305-O conveys a unique set of multiple wavelengths of CW laser light to a corresponding one of the O optical inputs 309-1 to 309-O of the O×N star coupler 307, such that any given one of the O optical inputs 309-1 to 309-O receives a mutually exclusive set of CW laser light wavelengths relative to the others of the O optical inputs 309-1 to 309-O. The O×N star coupler 307 is configured to convey each of the CW laser light wavelengths received on each of the O optical inputs 309-1 to 309-O to each of a number N of optical outputs 311-1 to 311-N of the O×N star coupler 307. In this manner, each of the N optical outputs 311-1 to 311-N conveys all M of the wavelengths of CW laser light received across all of the O optical inputs 309-1 to 309-O, which corresponds to all M wavelengths of light (λ1, to λM) received on optical input channels 1 to M.
As discussed above, in the M×N optical distribution network 300, M unique wavelength (λ1, to λM) channels are routed into a network of P MUX stages 301-1 to 301-P, where P is greater than or equal to one. The sequence of the M light wavelengths conveyed through the M optical input channels does not necessarily match the optical input channel sequence. More specifically, the values of the M light wavelengths conveyed through the M optical input channels do not necessarily increase or decrease monotonically with the optical input channel number. After the P MUX stages 301-1 to 301-P, the M light wavelengths are combined into 0 intermediate optical output ports 305-1 to 305-O, where each of the O intermediate optical output ports 305-1 to 305-O conveys a unique and mutually exclusive subset of the M input wavelengths. The light conveyed through the O intermediate optical output ports 305-1 to 305-O is then distributed to the N optical outputs 311-1 to 311-N by the O×N star coupler 307, such that each of the N optical outputs 311-1 to 311-N conveys all M light wavelengths (λ1, to λM) that were received across the M optical input channels. Therefore, the M×N optical distribution network 300 includes an M×O cascaded MUX network (the fore-positioned optical MUX section 313) having 0 intermediate optical outputs 305-1 to 305-O, where O is greater than one and where each of the O intermediate optical outputs 305-1 to 305-O conveys a unique subset of the M input light wavelengths. Also, within the M×N optical distribution network 300, the M×O cascaded MUX network (the fore-positioned optical MUX section 313) is followed by the O×N star coupler 307 (the optical coupler section 315), where N is greater than or equal to 0.
As compared to the M×1 cascaded MUX network (such as the M×1 cascaded MUX network 200 shown in
In the optical distribution network 300, each of the plurality of optical inputs (303i1-1-m and 303i2-1-m, where m is 1 to (M/2)) of the fore-positioned optical multiplexer section 313 is configured to receive a respective one of a plurality of input light signals of different wavelengths (λ1 to λM). The fore-positioned optical multiplexer section 313 is configured to multiplex a unique subset of the plurality of input light signals onto each of the plurality of intermediate optical outputs (305-1 to 305-O). The unique subset of the plurality of input light signals multiplexed on any given one of the plurality of intermediate optical outputs (305-1 to 305-O) is mutually exclusive with respect to the plurality of input light signals multiplexed on others of the plurality of intermediate optical outputs (305-1 to 305-O). The optical coupler section 315 is configured to distribute a portion of each light signal received at each of the plurality of optical inputs (309-1 to 309-O) of the optical coupler section 315 to each and every one of the plurality of optical outputs (311-1 to 311-N) of the optical coupler section 315. In some embodiments, the optical coupler section 315 is implemented as a free-space optical star coupler. In some embodiments, the optical coupler section 315 is implemented as a network of two-by-two optical couplers.
The fore-positioned optical multiplexer section 313 includes the number (P) of optical multiplexer stages (301-1 to 301-P). The number (P) is equal to a first value divided by a logarithm of two, where the first value is a logarithm of a second value, and where the second value is equal to the number (M) of the plurality of optical inputs (303i1-1-m and 303i2-1-m, where m is 1 to (M/2)) of the fore-positioned optical multiplexer section 313 divided by the number (O) of the plurality of intermediate optical outputs (305-1 to 305-O) of the fore-positioned optical multiplexer section 313. Each of the number (P) of optical multiplexer stages (301-1 to 301-P) includes a number (KS) of two-to-one optical multiplexers 303-S-Y, where (S) is an integer sequence number of a given one of the number (P) of optical multiplexer stages (301-1 to 301-P) counting from a first one of the number (P) of optical multiplexer stages (301-1 to 301-P) to a last one of the number (P) of optical multiplexer stages (301-1 to 301-P), and where Y is a multiplexer number from 1 to (M/2P) within the S-th one of the optical multiplexer stages (301-1 to 301-P). The first one of the number (P) of optical multiplexer stages (301-1 to 301-P) has optical inputs optically connected to the number (M) of the plurality of optical inputs (303i1-1-m and 303i2-1-m, where m is 1 to (M/2)) of the fore-positioned optical multiplexer section 313. The last one of the number (P) of optical multiplexer stages (301-1 to 301-P) has optical outputs optically connected to the number (0) of the plurality of intermediate optical outputs (305-1 to 305-O) of the fore-positioned optical multiplexer section 313. The number (KS) is equal to the number (M) of the plurality of optical inputs (303i1-1-m and 303i2-1-m, where m is 1 to (M/2)) of the fore-positioned optical multiplexer section 313 divided by a value equal to 2S.
Each of the number (KS) of two-to-one optical multiplexers 303-S-Y includes a first optical input, a second optical input, and an optical output. Each of the number (KS) of two-to-one optical multiplexers 303-S-Y is configured to combine light signals received on its first and second optical inputs onto its optical output. Each of a number (K1) of two-to-one optical multiplexers in the first optical multiplexer stage of the number (P) of optical multiplexer stages is configured to have a first optical wavelength passband for its first optical input and a second optical wavelength passband for its second optical input, where the second optical wavelength passband is different than the first optical wavelength passband. In some embodiments, the first optical wavelength passband and the second optical wavelength passband correspond to non-sequential channel wavelengths of continuous wave laser light input to the optical distribution network.
The MUX stage 301-P (which is the first and last MUX stage) in the 8×4 optical distribution network 300A includes four 2-to-1 MUX's 303-P-1, 303-P-2, 303-P-3, and 303-P-4. In some embodiments, each of the MUX's 303-P-1 to 303-P-4 is implemented as an MZI. Each of the four MUX's 303-P-1 to 303-P-4 has a respective first optical input 303i1-P-x, a respective second optical input 303i2-P-x, and a respective optical output 305-x, where x is the integer number of a given one of the MUX's 303-P-1 to 303-P-4. The ordering of the CW light wavelengths of the eight optical input channels (Channel 1 to Channel 8) is λ6, λ2, λ4, λ5, λ1, λ5, λ3, λ7, respectively, so as to match the MUX acceptance wavelengths of the MUX's 303-P-1 to 303-P-4. In this manner, the first MUX 303-P-1 combines the light wavelengths λ2 and λ6 onto the optical output 305-1. The second MUX 303-P-2 combines the light wavelengths λ4 and λ8 onto the optical output 305-2. The third MUX 303-P-3 combines the light wavelengths λ1 and λ5 onto the optical output 305-3. And, the fourth MUX 303-P-4 combines the light wavelengths λ3 and λ7 onto the optical output 305-4. Therefore, the two light wavelengths on each of the optical outputs 305-1 to 305-4 are separated from each other by four channel-to-channel light wavelength spacings.
The 4×4 star coupler 307A includes a first 2×2 optical coupler 401, a second 2×2 optical coupler 402, a third 2×2 optical coupler 403, and a fourth 2×2 optical coupler 404. The first 2×2 optical coupler 401 has a first optical input 309-1 optically connected to the optical output 305-1 of the first MUX 303-P-1, and a second optical input 309-2 optically connected to the optical output 305-2 of the second MUX 303-P-2. In this manner the first 2×2 optical coupler 401 receives the two CW laser light wavelengths λ2 and λ6 on the first optical input 309-1, and receives the two CW laser light wavelengths λ4 and λ8 on the second optical input 309-2. The first 2×2 optical coupler 401 has a first optical output 401o1 and a second optical output 401o2. The first 2×2 optical coupler 401 is configured to combine all of the light wavelengths received on the first optical input 309-1 and the second optical input 309-2 onto each of the two optical outputs 401o1 and 401o2. In this manner, each of the four CW laser light wavelengths λ2, λ4, λ6, and λ8 is output through each of the first optical output 401o1 and the second optical output 401o2.
The second 2×2 optical coupler 402 has a first optical input 309-3 optically connected to the optical output 305-3 of the third MUX 303-P-3, and a second optical input 309-4 optically connected to the optical output 305-4 of the fourth MUX 303-P-4. In this manner the second 2×2 optical coupler 402 receives the two CW laser light wavelengths λ1 and λ5 on the first optical input 309-3, and receives the two CW laser light wavelengths λ3 and λ7 on the second optical input 309-4. The second 2×2 optical coupler 402 has a first optical output 402o1 and a second optical output 402o2. The second 2×2 optical coupler 402 is configured to combine all of the CW laser light wavelengths received on the first optical input 309-3 and the second optical input 309-4 onto each of the two optical outputs 402o1 and 402o2. In this manner, each of the four CW laser light wavelengths λ1, λ3, λ5, and λ7 is output through each of the first optical output 402o1 and the second optical output 402o2.
The third 2×2 optical coupler 403 has a first optical input 403i1 optically connected to the first optical output 401o1 of the first 2×2 optical coupler 401, and a second optical input 403i2 optically connected to the first optical output 402o1 of the second 2×2 optical coupler 402. In this manner the third 2×2 optical coupler 403 receives the four CW laser light wavelengths λ2, λ4, λ6, and λ8 on the first optical input 403i1, and receives the four CW laser light wavelengths λ1, λ3, λ5, and λ7 on the second optical input 403i2. The third 2×2 optical coupler 403 has a first optical output 311-1 and a second optical output 311-2. The third 2×2 optical coupler 403 is configured to combine all of the CW laser light wavelengths received on the first optical input 403i1 and the second optical input 403i2 onto each of the two optical outputs 311-1 and 311-2. In this manner, each of the eight CW laser light wavelengths λ1, λ2, λ3, λ4, λ5, λ6, λ7, and λ8 is output through each of the first optical output 311-1 and the second optical output 311-2 of the third 2×2 optical coupler 403.
The fourth 2×2 optical coupler 404 has a first optical input 404i1 optically connected to the second optical output 401o2 of the first 2×2 optical coupler 401, and a second optical input 404i2 optically connected to the second optical output 402o2 of the second 2×2 optical coupler 402. In this manner the fourth 2×2 optical coupler 404 receives the four CW laser light wavelengths λ2, λ4, λ6, and λ8 on the first optical input 404i1, and receives the four CW laser light wavelengths λ1, λ3, λ5, and λ7 on the second optical input 404i2. The fourth 2×2 optical coupler 404 has a first optical output 311-3 and a second optical output 311-4. The fourth 2×2 optical coupler 404 is configured to combine all of the CW laser light wavelengths received on the first optical input 404i1 and the second optical input 404i2 onto each of the two optical outputs 311-3 and 311-4. In this manner, each of the eight CW laser light wavelengths λ1, λ2, λ3, λ4, λ5, λ6, λ7, and λ8 is output through each of the first optical output 311-3 and the second optical output 311-4 of the fourth 2×2 optical coupler 404.
An optical waveguide crossing 409 is implemented within the 4×4 star coupler 307A to provide for optical connection between the second optical output 401o2 of the first 2×2 optical coupler 401 and the first optical input 404i1 of the fourth 2×2 optical coupler 404, while also providing for optical connection between the first optical output 402o1 of the second 2×2 optical coupler 402 and the second optical input 403i2 of the third 2×2 optical coupler 403. The optical waveguide crossing 409 is configured to ensure that light traveling from the second optical output 401o2 of the first 2×2 optical coupler 401 to the first optical input 404i1 of the fourth 2×2 optical coupler 404 does not interfere with by light traveling from the first optical output 402o1 of the second 2×2 optical coupler 402 to the second optical input 403i2 of the third 2×2 optical coupler 403, and vice-versa.
The laser array 101 includes the number M of lasers, where each of the lasers 1 to M is tuned to output a unique wavelength of CW light into a respective one of M optical input channels (Channel 1 to Channel M) of the M×N optical distribution network 300. In this manner, the set of M lasers is tuned to collectively output M different wavelengths (λ1 to λM) of CW laser light, with each laser outputting a different one of the M different wavelengths (λ1 to λM) of CW laser light. In some embodiments, each of the M lasers in the laser array 101 is a distributed feedback (DFB) laser.
In some embodiments, at least one of the M lasers in the laser array 101 is thermally coupled to at least one other of the M lasers in the laser array, such that a change in temperature of one of the thermally coupled lasers results in a change in temperature of the at least one other of the thermally coupled lasers. In some embodiments, the M lasers in the laser array 101 are thermally coupled together in a collective manner, such that the respective temperatures of the M lasers change/drift together. In some embodiments, each of the M lasers in the laser array 101 is thermally connected to a common thermally conductive substrate/plate 501, such that the temperature of each of the M lasers in the laser array 101 is normalized to an average temperature based on the collective thermal output of the M lasers in the laser array 101, and such that temperatures of the M lasers in the laser array 101 drift together in direction and magnitude. In this manner, a temperature-induced wavelength variation will be substantially the same across the M lasers in the laser array 101, which serves to maintain relative wavelength spacings from laser-to-laser as the temperature-induced wavelength variation occurs. In some embodiments, the plurality of lasers (Laser 1 to Laser M) are arranged in the laser array 101 such that a sequence of the plurality of wavelengths of continuous wave laser light (as output by the Lasers 1 to M) is non-monotonically ordered across the laser array 101.
In some embodiments, the M×N optical distribution network 300 is a photonic integrated circuit (PIC) integrated on a semiconductor electro-optical chip with M optical input channels (Channel 1 to Channel M) and N optical output channels (Output 1 to Output N). The M optical input channels (Channel 1 to Channel M) respectively correspond to the optical inputs 303i1-1, 303i2-1-1 to 303i1-1-(M/2), 303i2-1-(M/2) of the MUX's 303-1-1 to 303-1-(M/2) in the first MUX stage 301-1 of the fore-positioned optical MUX section 313 of the M×N optical distribution network 300. The N optical output channels (Output 1 to Output N) respectively correspond to the N optical outputs 311-1 to 311-N of the optical coupler section 315 of the M×N optical distribution network 300. The M×N optical distribution network 300 is configured to distribute light from each of the M optical input channels (Channel 1 to Channel M) to all of the N optical output channels (Output 1 to Output N), such that each and every one of the N optical output channels (Output 1 to Output N) conveys CW laser light of all M different wavelengths (λ1 to λM) as output by the laser array 101. The plurality of optical outputs (311-1 to 311-N) of the optical coupler section 315 respectively correspond to each of a plurality of optical outputs of the optical distribution network 300 and a plurality of outputs of the laser module 500.
In some embodiments, the laser array 101 is directly optically coupled to the M×N optical distribution network 300 without any intermediate light guiding components, such as optical fibers or optical waveguides, such that CW laser light from each of the M lasers in the laser array 101 is transmitted directly into the corresponding one of the M optical input channels (Channel 1 to Channel M) in the M×N optical distribution network 300 chip. For example, Laser 1 transmits CW laser light directly into optical input Channel 1, Laser 2 transmits CW laser light directly into optical input Channel 2, and so on, with Laser M transmitting CW laser light directly into optical input Channel M. In these embodiments, each of the M lasers in the laser array 101 is optically coupled directly to the corresponding physical optical channel in the M×N optical distribution network 300. It should be understood, however, that in various embodiments, essentially any method or technique of coupling light may be used to optically couple each of the M lasers in the laser array 101 to the corresponding one of the M optical input channels (Channel 1 to Channel M) in the M×N optical distribution network 300. For example, in some embodiments, optical coupling of the M lasers in the laser array 101 to the corresponding M optical input channels (Channel 1 to Channel M) in the M×N optical distribution network 300 is done by optical vertical grating coupling, optical edge coupling, and/or lens-based optical coupling, among other techniques, by way of example.
In some embodiments, the MUX's 303-1-1 to 303-1-(M/2) in the first MUX stage 301-1 of the fore-positioned optical MUX section 313 of the M×N optical distribution network 300 may require an input light wavelength sequence that is not linearly or monotonically varying (increasing/decreasing) with the physical optical input channel number. In these embodiments, the wavelengths of the CW laser light output by the M lasers in the laser array 101 are set to substantially match the peaks of the wavelength acceptance passbands of the MUX's 303-1-1 to 303-1-(M/2) in the first MUX stage 301-1 of the fore-positioned optical MUX section 313 of the M×N optical distribution network 300. Specifically, the Laser 1 in the laser array 101 is set to output CW laser light at a wavelength that substantially matches the peak of the wavelength acceptance passband of the first optical input 303i1-1-1 of the first MUX 303-1-1 of the first MUX stage 301-1, with the Laser 1 being directly optically coupled to the first optical input 303i1-1-1 of the first MUX 303-1-1 of the first MUX stage 301-1. Continuing on, the Laser 2 in the laser array 101 is set to output CW laser light at a wavelength that substantially matches the peak of the wavelength acceptance passband of the second optical input 303i2-1-1 of the first MUX 303-1-1 of the first MUX stage 301-1, with the Laser 2 being directly optically coupled to the second optical input 303i2-1-1 of the first MUX 303-1-1 of the first MUX stage 301-1. Continuing on, the Laser 3 in the laser array 101 is set to output CW laser light at a wavelength that substantially matches the peak of the wavelength acceptance passband of the first optical input 303i1-1-2 of the second MUX 303-1-2 of the first MUX stage 301-1, with the Laser 3 being directly optically coupled to the first optical input 303i1-1-2 of the second MUX 303-1-2 of the first MUX stage 301-1. Continuing on, the Laser 4 in the laser array 101 is set to output CW laser light at a wavelength that substantially matches the peak of the wavelength acceptance passband of the second optical input 303i2-1-2 of the second MUX 303-1-2 of the first MUX stage 301-1, with the Laser 4 being directly optically coupled to the second optical input 303i2-1-2 of the second MUX 303-1-2 of the first MUX stage 301-1, and so on. Then, finally, the Laser M in the laser array 101 is set to output CW laser light at a wavelength that substantially matches the peak of the wavelength acceptance passband of the second optical input 303i2-1-(M/2) of the last, i.e., (M/2), MUX 303-1-(M/2) of the first MUX stage 301-1, with the Laser M being directly optically coupled to the second optical input 303i2-1-(M/2) of the last MUX 303-1-(M/2) of the first MUX stage 301-1. In some embodiments, the laser array 101 is optically interfaced with the optical distribution network 300 such that the plurality of wavelengths of continuous wave laser light are transmitted directly from the plurality of lasers (Laser 1 to Laser M) into the plurality of optical inputs (303i1-1, 303i2-1-1 to 303i1-1-(M/2), 303i2-1-(M/2)) of the fore-positioned optical multiplexer section 313.
It should be understood that because the wavelengths of the CW laser light output by the M lasers in the laser array 101 are set to substantially match the peaks of the wavelength acceptance passbands of the MUX's 303-1-1 to 303-1-(M/2) in the first MUX stage 301-1 of the fore-positioned optical MUX section 313 of the M×N optical distribution network 300, the wavelengths of the CW laser light output by the M lasers in the laser array 101 may not vary in a monotonic manner from Laser 1 to Laser M in the laser array 101. Therefore, it should be appreciated that the laser array 101 is configured differently from conventional laser arrays that have only monotonically increasing or monotonically decreasing laser light output wavelengths along a sequence or series of lasers.
In order to optically connect a laser array that has only monotonically increasing or monotonically decreasing laser light output wavelengths along its sequence/series of lasers to the M×N optical distribution network 300 that has a non-monotonic input wavelength sequence, it would be necessary to route optical paths across each other between the laser array 101 and the M×N optical distribution network 300, such as by routing light through optical fibers connected between the laser array 101 and the M×N optical distribution network 300. In some embodiments, the non-monotonic ordering of the sequence of the plurality of wavelengths of CW laser light across the laser array 101 matches an ordering of wavelength acceptance passbands of the plurality of optical inputs (303i1-1, 303i2-1-1 to 303i1-1-(M/2), 303i2-1-(M/2)) of the fore-positioned optical multiplexer section 313. By setting each of the M lasers in the laser array 101 to output CW light having a particular wavelength that substantially matches the peak of the wavelength acceptance passband of the corresponding one of the M optical inputs of the M×N optical distribution network 300, it is possible to avoid having to route optical paths across one another in optically connecting the laser array 101 to the M×N optical distribution network 300. This is beneficial since routing optical paths across one another could result in additional optical insertion loss, which could occur, for example, if the optical routing had to be done in a single waveguiding layer in an integrated optical chip and correspondingly require the use of optical waveguide crossings, which typically have non-zero optical insertion loss.
In some embodiments, the M×N optical distribution network 300 is implemented to include the fore-positioned optical MUX section 313 including at least one MUX stage 301-x, where x is an integer from 1 to P, and where P is greater than or equal to one. However, in other embodiments, a variation of the M×N optical distribution network 300 is implemented without the fore-positioned optical MUX section 313, such that P is equal to zero. In these embodiments where P is equal to zero, the number O of intermediate optical output ports 305-1 to 305-O of the M×N optical distribution network 300 effectively becomes the number M of optical input channels (Channel 1 to Channel M) of the M×N optical distribution network 300. In these embodiments, with the fore-positioned optical MUX section 313 removed from the M×N optical distribution network 300, the number M of optical input channels (Channel 1 to Channel M) are respectively optically connected to the number O of optical inputs 309-1 to 309-O of the optical coupler section 315 of the M×N optical distribution network 300, i.e., such that the number M of optical input channels (Channel 1 to Channel M) are respectively optically connected to the number O of optical inputs of the O×N star coupler 307.
The laser array 101 of
In some embodiments, the laser array 101 is directly coupled to the 8×8 optical distribution network 600 without any intermediate light guiding components, such as optical fibers or optical waveguides, such that CW laser light from each of the eight lasers (Laser 1 to Laser 8) in the laser array 101 radiates directly into the corresponding one of the eight optical input channels (Channel 1 to Channel M) in the 8×8 optical distribution network 600. It should be understood, however, that in various embodiments, essentially any method or technique of coupling light may be used to optically couple each of the eight lasers (Laser 1 to Laser 8) in the laser array 101 to the corresponding one of the eight optical input channels (Channel 1 to Channel M) in the 8×8 optical distribution network 600, such as vertical grating optical coupling, optical edge coupling, and/or lens-based optical coupling, among others, by way of example.
The 8×8 optical distribution network 600 is configured to distribute light from each and every one of the eight optical input channels (Channel 1 to Channel 8) to each one of the eight optical output channels 311-1 to 311-8, such that each and every one of the eight optical output channels 311-1 to 311-8 conveys CW laser light of all eight different wavelengths (λ1 to λ8) that are output by the laser array 101 and input to the 8×8 optical distribution network 600. The eight optical input channels (Channel 1 to Channel 8) respectively correspond to the optical inputs 309-1 to 309-O of the 8×8 optical distribution network 600, where O is eight. The eight optical output channels 311-1 to 311-8 respectively correspond to the optical outputs 311-1 to 311-N of the 8×8 optical distribution network 600, where N is eight.
In the 8×8 optical distribution network 600, the optical coupler section 315 is implemented as an 8×8 star coupler 307B that includes twelve 2×2 optical couplers 601-1 to 601-12. The first 2×2 optical coupler 601-1 has a first optical input 601i1-1 that is optically connected to the first optical input channel (Channel 1), and a second optical input 601i2-1 that is optically connected to the second optical input channel (Channel 2). In this manner the first 2×2 optical coupler 601-1 receives the CW laser light wavelength λ1 on the first optical input 601i1-1, and receives the CW laser light wavelength λ2 on the second optical input 601i2-1. The first 2×2 optical coupler 601-1 has a first optical output 601o1-1 and a second optical output 601o2-1. The first 2×2 optical coupler 601-1 is configured to combine the CW laser light wavelength λ1 received on the first optical input 601i1-1 and the CW laser light wavelength λ2 received on the second optical input 601i2-1 onto each of the two optical outputs 601o1-1 and 601o2-1. In this manner, each of the two CW laser light wavelengths λ1 and λ2 is output through each of the first optical output 601o1-1 and the second optical output 601o2-1.
The second 2×2 optical coupler 601-2 has a first optical input 601i1-2 that is optically connected to the third optical input channel (Channel 3), and a second optical input 601i2-2 that is optically connected to the fourth optical input channel (Channel 4). In this manner the second 2×2 optical coupler 601-2 receives the CW laser light wavelength λ3 on the first optical input 601i1-2, and receives the CW laser light wavelength λ4 on the second optical input 601i2-2. The second 2×2 optical coupler 601-2 has a first optical output 601o1-2 and a second optical output 601o2-2. The second 2×2 optical coupler 601-2 is configured to combine the CW laser light wavelength λ3 received on the first optical input 601i1-2 and the CW laser light wavelength λ4 received on the second optical input 601i2-2 onto each of the two optical outputs 601o1-2 and 601o2-2. In this manner, each of the two CW laser light wavelengths λ3 and λ4 is output through each of the first optical output 601o1-2 and the second optical output 601o2-2.
The third 2×2 optical coupler 601-3 has a first optical input 601i1-3 that is optically connected to the fifth optical input channel (Channel 5), and a second optical input 601i2-3 that is optically connected to the sixth optical input channel (Channel 6). In this manner the third 2×2 optical coupler 601-3 receives the CW laser light wavelength λ5 on the first optical input 601i1-3, and receives the CW laser light wavelength λ6 on the second optical input 601i2-3. The third 2×2 optical coupler 601-3 has a first optical output 601o1-3 and a second optical output 601o2-3. The third 2×2 optical coupler 601-3 is configured to combine the CW laser light wavelength λ5 received on the first optical input 601i1-3 and the CW laser light wavelength λ6 received on the second optical input 601i2-3 onto each of the two optical outputs 601o1-3 and 601o2-3. In this manner, each of the two CW laser light wavelengths λ5 and λ6 is output through each of the first optical output 601o1-3 and the second optical output 601o2-3.
The fourth 2×2 optical coupler 601-4 has a first optical input 601i1-4 that is optically connected to the seventh optical input channel (Channel 7), and a second optical input 601i2-4 that is optically connected to the eighth optical input channel (Channel 8). In this manner the fourth 2×2 optical coupler 601-4 receives the CW laser light wavelength λ7 on the first optical input 601i1-4, and receives the CW laser light wavelength λ8 on the second optical input 601i2-4. The fourth 2×2 optical coupler 601-4 has a first optical output 601o1-4 and a second optical output 601o2-4. The fourth 2×2 optical coupler 601-4 is configured to combine the CW laser light wavelength λ7 received on the first optical input 601i1-4 and the CW laser light wavelength A8 received on the second optical input 601i2-4 onto each of the two optical outputs 601o1-4 and 601o2-4. In this manner, each of the two CW laser light wavelengths λ7 and λ8 is output through each of the first optical output 601o1-4 and the second optical output 601o2-4.
The fifth 2×2 optical coupler 601-5 has a first optical input 601i1-5 optically connected to the first optical output 601o1-1 of the first 2×2 optical coupler 601-1, and a second optical input 601i2-5 optically connected to the first optical output 601o1-2 of the second 2×2 optical coupler 601-2. In this manner the fifth 2×2 optical coupler 601-5 receives the two CW laser light wavelengths λ1 and λ2 on the first optical input 601i1-5, and receives the two CW laser light wavelengths λ3 and λ4 on the second optical input 601i2-5. The fifth 2×2 optical coupler 601-5 has a first optical output 601o1-5 and a second optical output 601o2-5. The fifth 2×2 optical coupler 601-5 is configured to combine all of the CW laser light wavelengths received on the first optical input 601i1-5 and the second optical input 601i2-5 onto each of the two optical outputs 601o1-5 and 601o2-5. In this manner, each of the four CW laser light wavelengths λ1, λ2, λ3, and λ4 is output through each of the first optical output 601o1-5 and the second optical output 601o2-5 of the fifth 2×2 optical coupler 601-5.
The sixth 2×2 optical coupler 601-6 has a first optical input 601i1-6 optically connected to the first optical output 601o1-3 of the third 2×2 optical coupler 601-3, and a second optical input 601i2-6 optically connected to the first optical output 601o1-4 of the fourth 2×2 optical coupler 601-4. In this manner the sixth 2×2 optical coupler 601-6 receives the two CW laser light wavelengths λ5 and λ6 on the first optical input 601i1-6, and receives the two CW laser light wavelengths λ7 and λ8 on the second optical input 601i2-6. The sixth 2×2 optical coupler 601-6 has a first optical output 601o1-6 and a second optical output 601o2-6. The sixth 2×2 optical coupler 601-6 is configured to combine all of the CW laser light wavelengths received on the first optical input 601i1-6 and the second optical input 601i2-6 onto each of the two optical outputs 601o1-6 and 601o2-6. In this manner, each of the four CW laser light wavelengths A5, λ6, λ7, and λ8 is output through each of the first optical output 601o1-6 and the second optical output 601o2-6 of the sixth 2×2 optical coupler 601-6.
The seventh 2×2 optical coupler 601-7 has a first optical input 601i1-7 optically connected to the second optical output 601o2-1 of the first 2×2 optical coupler 601-1, and a second optical input 601i2-7 optically connected to the second optical output 601o2-2 of the second 2×2 optical coupler 601-2. In this manner the seventh 2×2 optical coupler 601-7 receives the two CW laser light wavelengths λ1 and λ2 on the first optical input 601i1-7, and receives the two CW laser light wavelengths λ3 and λ4 on the second optical input 601i2-7. The seventh 2×2 optical coupler 601-7 has a first optical output 601o1-7 and a second optical output 601o2-7. The seventh 2×2 optical coupler 601-7 is configured to combine all of the CW laser light wavelengths received on the first optical input 601i1-7 and the second optical input 601i2-7 onto each of the two optical outputs 601o1-7 and 601o2-7. In this manner, each of the four CW laser light wavelengths λ1, λ2, λ3, and λ4 is output through each of the first optical output 601o1-7 and the second optical output 601o2-7 of the seventh 2×2 optical coupler 601-7.
The eighth 2×2 optical coupler 601-8 has a first optical input 601i1-8 optically connected to the second optical output 601o2-3 of the third 2×2 optical coupler 601-3, and a second optical input 601i2-8 optically connected to the second optical output 601o2-4 of the fourth 2×2 optical coupler 601-4. In this manner the eighth 2×2 optical coupler 601-8 receives the two CW laser light wavelengths λ5 and λ6 on the first optical input 601i1-8, and receives the two CW laser light wavelengths λ7 and λ8 on the second optical input 601i2-8. The eighth 2×2 optical coupler 601-8 has a first optical output 601o1-8 and a second optical output 601o2-8. The eighth 2×2 optical coupler 601-8 is configured to combine all of the CW laser light wavelengths received on the first optical input 601i1-8 and the second optical input 601i2-8 onto each of the two optical outputs 601o1-8 and 601o2-8. In this manner, each of the four CW laser light wavelengths A5, λ6, λ7, and λ8 is output through each of the first optical output 601o1-8 and the second optical output 601o2-8 of the eighth 2×2 optical coupler 601-8.
The 8×8 star coupler 307B includes six optical waveguide crossings 603-1 to 603-6 to enable optical routings between optical outputs of the 2×2 optical couplers 601-1 to 601-4 and optical inputs of the 2×2 optical couplers 601-5 to 601-8 as described above. The optical waveguide crossing 603-1 enables optical routing between the first optical output 601o1-2 of the second 2×2 optical coupler 601-2 and the second optical input 601i2-5 of the fifth 2×2 optical coupler 601-5. The optical waveguide crossings 603-2 and 603-4 enable optical routing between the first optical output 601o1-3 of the third 2×2 optical coupler 601-3 and the first optical input 601i1-6 of the sixth 2×2 optical coupler 601-6. The optical waveguide crossings 603-3, 603-5, and 603-6 enable optical routing between the first optical output 601o1-4 of the fourth 2×2 optical coupler 601-4 and the second optical input 601i2-6 of the sixth 2×2 optical coupler 601-6. The optical waveguide crossings 603-1, 603-4, and 603-6 enable optical routing between the second optical output 601o2-1 of the first 2×2 optical coupler 601-1 and the first optical input 601i1-7 of the seventh 2×2 optical coupler 601-7. The optical waveguide crossings 603-2 and 603-5 enable optical routing between the second optical output 601o2-2 of the second 2×2 optical coupler 601-2 and the second optical input 601i2-7 of the seventh 2×2 optical coupler 601-7. The optical waveguide crossing 603-3 enables optical routing between the second optical output 601o2-3 of the third 2×2 optical coupler 601-3 and the first optical input 601i1-8 of the eighth 2×2 optical coupler 601-8. Each of the optical waveguide crossings 603-1 to 603-6 is configured to ensure that CW laser light traveling through each of two crossing optical waveguides does not interfere with each other.
The ninth 2×2 optical coupler 601-9 has a first optical input 601i1-9 optically connected to the first optical output 601o1-5 of the fifth 2×2 optical coupler 601-5, and a second optical input 601i2-9 optically connected to the first optical output 601o1-6 of the sixth 2×2 optical coupler 601-6. In this manner the ninth 2×2 optical coupler 601-9 receives the four CW laser light wavelengths λ1, λ2, λ3, and λ4 on the first optical input 601i1-9, and receives the four CW laser light wavelengths λ5, λ6, λ7, and λ8 on the second optical input 601i2-9. The ninth 2×2 optical coupler 601-9 has a first optical output 601o1-9 and a second optical output 601o2-9. The ninth 2×2 optical coupler 601-9 is configured to combine all of the light wavelengths received on the first optical input 601i1-9 and the second optical input 601i2-9 onto each of the two optical outputs 601o1-9 and 601o2-9. In this manner, each of the eight CW laser light wavelengths λ1, λ2, λ3, λ4, λ5, λ6, λ7, and λ8 is output through each of the first optical output 601o1-9 and the second optical output 601o2-9 of the ninth 2×2 optical coupler 601-9, which correspond to the optical outputs 311-1 and 311-2, respectively, of the 8×8 optical distribution network 600.
The tenth 2×2 optical coupler 601-10 has a first optical input 601i1-10 optically connected to the second optical output 601o2-5 of the fifth 2×2 optical coupler 601-5, and a second optical input 601i2-10 optically connected to the second optical output 601o2-6 of the sixth 2×2 optical coupler 601-6. In this manner the tenth 2×2 optical coupler 601-10 receives the four CW laser light wavelengths λ1, λ2, λ3, and λ4 on the first optical input 601i1-10, and receives the four CW laser light wavelengths λ5, λ6, λ7, and λ8 on the second optical input 601i2-10. The tenth 2×2 optical coupler 601-10 has a first optical output 601o1-10 and a second optical output 601o2-10. The tenth 2×2 optical coupler 601-10 is configured to combine all of the CW laser light wavelengths received on the first optical input 601i1-10 and the second optical input 601i2-10 onto each of the two optical outputs 601o1-10 and 601o2-10. In this manner, each of the eight CW laser light wavelengths λ1, λ2, λ3, λ4, λ5, λ6, λ7, and λ8 is output through each of the first optical output 601o1-10 and the second optical output 601o2-10 of the tenth 2×2 optical coupler 601-10, which correspond to the optical outputs 311-3 and 311-4, respectively, of the 8×8 optical distribution network 600.
The eleventh 2×2 optical coupler 601-11 has a first optical input 601i1-11 optically connected to the first optical output 601o1-7 of the seventh 2×2 optical coupler 601-7, and a second optical input 601i2-11 optically connected to the first optical output 601o1-8 of the eighth 2×2 optical coupler 601-8. In this manner the eleventh 2×2 optical coupler 601-11 receives the four CW laser light wavelengths λ1, λ2, λ3, and λ4 on the first optical input 601i1-11, and receives the four CW laser light wavelengths λ5, λ6, λ7, and λ8 on the second optical input 601i2-11. The eleventh 2×2 optical coupler 601-11 has a first optical output 601o1-11 and a second optical output 601o2-11. The eleventh 2×2 optical coupler 601-11 is configured to combine all of the CW laser light wavelengths received on the first optical input 601i1-11 and the second optical input 601i2-11 onto each of the two optical outputs 601o1-11 and 601o2-11. In this manner, each of the eight CW laser light wavelengths λ1, λ2, λ3, λ4, λ5, λ6, λ7, and λ8 is output through each of the first optical output 601o1-11 and the second optical output 601o2-11 of the eleventh 2×2 optical coupler 601-11, which correspond to the optical outputs 311-5 and 311-6, respectively, of the 8×8 optical distribution network 600.
The twelfth 2×2 optical coupler 601-12 has a first optical input 601i1-12 optically connected to the second optical output 601o2-7 of the seventh 2×2 optical coupler 601-7, and a second optical input 601i2-12 optically connected to the second optical output 601o2-8 of the eighth 2×2 optical coupler 601-8. In this manner the twelfth 2×2 optical coupler 601-12 receives the four CW laser light wavelengths λ1, λ2, λ3, and λ4 on the first optical input 601i1-12, and receives the four CW laser light wavelengths A5, λ6, λ7, and λ8 on the second optical input 601i2-12. The twelfth 2×2 optical coupler 601-12 has a first optical output 601o1-12 and a second optical output 601o2-12. The twelfth 2×2 optical coupler 601-12 is configured to combine all of the CW laser light wavelengths received on the first optical input 601i1-12 and the second optical input 601i2-12 onto each of the two optical outputs 601o1-12 and 601o2-12. In this manner, each of the eight CW laser light wavelengths λ1, λ2, λ3, λ4, λ5, λ6, λ7, and λ8 is output through each of the first optical output 601o1-12 and the second optical output 601o2-12 of the twelfth 2×2 optical coupler 601-12, which correspond to the optical outputs 311-7 and 311-8, respectively, of the 8×8 optical distribution network 600.
The 8×8 star coupler 307B also includes two more optical waveguide crossings 603-7 and 603-8 to enable optical routings between optical outputs of the 2×2 optical couplers 601-5 to 601-8 and optical inputs of the 2×2 optical couplers 601-9 to 601-12. The optical waveguide crossing 603-7 enables optical routing between the first optical output 601o1-6 of the sixth 2×2 optical coupler 601-6 and the second optical input 601i2-9 of the ninth 2×2 optical coupler 601-9. The optical waveguide crossing 603-7 also enables optical routing between the second optical output 601o2-5 of the fifth 2×2 optical coupler 601-5 and the first optical input 601i1-10 of the tenth 2×2 optical coupler 601-10. The optical waveguide crossing 603-8 enables optical routing between the first optical output 601o1-8 of the eighth 2×2 optical coupler 601-8 and the second optical input 601i2-11 of the eleventh 2×2 optical coupler 601-11. The optical waveguide crossing 603-8 also enables optical routing between the second optical output 601o2-7 of the seventh 2×2 optical coupler 601-7 and the first optical input 601i1-12 of the twelfth 2×2 optical coupler 601-12. Each of the optical waveguide crossings 603-7 and 603-8 is configured to ensure that CW laser light traveling through each of two crossing optical waveguides does not interfere with each other.
In various embodiments, the optical waveguide crossings 409 and 603-1 to 603-8 referred to herein can be implemented in many different ways, such as those described in the following references, by way of example, each of which is incorporated herein by reference: A) Y. Zhang et al., “A CMOS-Compatible, Low-Loss, and Low-Crosstalk Silicon Waveguide Crossing,” in IEEE Photonics Technology Letters, Vol. 25, No. 5, pp. 422-425, Mar. 1, 2013; B) H. Chen et al., “Low-Loss Multimode-Interference-Based Crossings for Silicon Wire Waveguides,” in IEEE Photonics Technology Letters, Vol. 18, No. 21, pp. 2260-2262, Nov. 1, 2006; C) H. Yang et al., “A Broadband, Low-Crosstalk and Low Polarization Dependent Silicon Nitride Waveguide Crossing Based on the Multimode-Interference,” Optics Communications, Vol. 450, pp. 28-33, 2019; D) P. Sanchis et al., “Highly Efficient Crossing Structure for Silicon-on-Insulator Waveguides,” Optics Letters, Vol. 34, pp. 2760-2762, 2009; E) W. Bogaerts et al., “Low-Loss, Low-Cross-Talk Crossings for Silicon-on-Insulator Nanophotonic Waveguides,” Optics Letters, Vol. 32, pp. 2801-2803, 2007; and F) C. H. Chen et al., “Taper-Integrated Multimode-Interference Based Waveguide Crossing Design,” in IEEE Journal of Quantum Electronics, Vol. 46, No. 11, pp. 1656-1661, November 2010.
In some embodiments, the plurality of lasers (Laser 1 to Laser M) are arranged in the laser array 101 such that a wavelength sequence of the plurality of input light signals of different wavelengths is non-monotonically ordered across the laser array 101 so as to match a corresponding non-monotonically ordered sequence of wavelength acceptance passbands across the plurality of optical inputs (303i1-1-m and 303i2-1-m, where m is 1 to (M/2)) of the fore-positioned optical multiplexer section 313. In some embodiments, both a non-monotonic ordering of the wavelength sequence of the plurality of input light signals across the laser array 101 and a corresponding non-monotonic ordering of wavelength acceptance passbands across the plurality of optical inputs (303i1-1-m and 303i2-1-m, where m is 1 to (M/2)) of the fore-positioned optical multiplexer section 313 are collectively defined so that a tolerance of the optical power at the optical outputs of the laser module 500 for temperature-induced wavelength variation is increased for each of the plurality of lasers (Laser 1 to Laser M) as compared with the tolerance of the optical power at the optical outputs of the laser module 500 for temperature-induced wavelength variation for each of the plurality of lasers (Laser 1 to Laser M) that exists with both a monotonic ordering of the wavelength sequence of the plurality of input light signals across the laser array 101 and a corresponding monotonic ordering of wavelength acceptance passbands across the plurality of optical inputs (303i1-1-m and 303i2-1-m, where m is 1 to (M/2)) of the fore-positioned optical multiplexer section 313. The tolerance of the optical power at the optical outputs of the laser module 500 refers to a tolerable impact of wavelength variation on the output optical power of the laser module 500 for each wavelength at each optical output port of the laser module 500. Temperature-induced wavelength variation for each of the plurality of lasers (Laser 1 to Laser M) is a contributor to variation in the output optical power of the laser module 500 for each wavelength at each optical output port of the laser module 500, where said variation in the output optical power at the optical outputs of the laser module 500 should be maintained within a specified acceptable power tolerance range.
In some embodiments, operating the fore-positioned optical multiplexer section 313 in the operation 705 includes conveying the plurality of input light signals as received at the plurality of optical inputs (303i1-1-m and 303i2-1-m, where m is 1 to (M/2)) of the fore-positioned optical multiplexer section 313 through the number (P) of optical multiplexer stages 301-1 to 301-P, where the number (P) is equal to a first value divided by a logarithm of two, where the first value is a logarithm of a second value, and where the second value is equal to the number (M) of the plurality of optical inputs (303i1-1-m and 303i2-1-m, where m is 1 to (M/2)) of the fore-positioned optical multiplexer section 313 divided by the number (O) of the plurality of intermediate optical outputs (305-1 to 305-O) of the fore-positioned optical multiplexer section 313, i.e., P=[log(M/O)/log(2)].
In some embodiments, each of the number (P) of optical multiplexer stages (301-1 to 301-P) includes a number (KS) of two-to-one optical multiplexers 303-S-Y, where S is an integer sequence number of a given one of the number (P) of optical multiplexer stages (301-1 to 301-P) counting from a first one of the number (P) of optical multiplexer stages (301-1 to 301-P) to a last one of the number (P) of optical multiplexer stages (301-1 to 301-P), and where Y is a multiplexer number from 1 to (M/2P) within the S-th one of the optical multiplexer stages (301-1 to 301-P). The first one of the number (P) of optical multiplexer stages (301-1 to 301-P) has optical inputs optically connected to the number (M) of the plurality of optical inputs (303i1-1-m and 303i2-1-m, where m is 1 to (M/2)) of the fore-positioned optical multiplexer section 313. The last one of the number (P) of optical multiplexer stages (301-1 to 301-P) has optical outputs optically connected to the number (O) of the plurality of intermediate optical outputs (305-1 to 305-O) of the fore-positioned optical multiplexer section 313. The number (KS) is equal to the number (M) of the plurality of optical inputs (303i1-1-m and 303i2-1-m, where m is 1 to (M/2)) of the fore-positioned optical multiplexer section 313 divided by a value equal to 2S. Each of the number (KS) of two-to-one optical multiplexers 303-S-Y includes a first optical input, a second optical input, and an optical output. The method includes operating each of the number (KS) of two-to-one optical multiplexers 303-S-Y to combine light signals received on its first and second optical inputs onto its optical output.
The foregoing description of the embodiments has been provided for purposes of illustration and description, and is not intended to be exhaustive or limiting. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. In this manner, one or more features from one or more embodiments disclosed herein can be combined with one or more features from one or more other embodiments disclosed herein to form another embodiment that is not explicitly disclosed herein, but rather that is implicitly disclosed herein. This other embodiment may also be varied in many ways. Such embodiment variations are not to be regarded as a departure from the disclosure herein, and all such embodiment variations and modifications are intended to be included within the scope of the disclosure provided herein.
Although some method operations may be described in a specific order herein, it should be understood that other housekeeping operations may be performed in between method operations, and/or method operations may be adjusted so that they occur at slightly different times or simultaneously or may be distributed in a system which allows the occurrence of the processing operations at various intervals associated with the processing, as long as the processing of the method operations are performed in a manner that provides for successful implementation of the method.
Although the foregoing embodiments have been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications can be practiced within the scope of the appended claims. Accordingly, the embodiments disclosed herein are to be considered as illustrative and not restrictive, and are therefore not to be limited to just the details given herein, but may be modified within the scope and equivalents of the appended claims.
This claims priority under 35 U.S.C. 119(e) to U.S. Provisional Patent Application No. 63/318,054, filed on Mar. 9, 2022, the disclosure of which is incorporated herein by reference in its entirety for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 63318054 | Mar 2022 | US |
