Patent Application
20130094806
The present application relates to optical signal conversion, in particular optical conversion between multi-mode single-wavelength signals and a single-mode multi-wavelength signal.
Parallel optical short-reach interconnects (OSRI) are typically used for high-performance computing (HPC) and data center interconnects. Short reach interconnects such as OSRI are typically less than 300 m in length. Long reach interconnects are typically greater than several km in length. To send traffic over a long haul (e.g. 10 km or more), a full electrical conversion of the outgoing signal is conventionally performed in order to ensure the signal conforms to the telecom transport equipment optical characteristics between the systems. Energy is consumed converting an optical signal (such as a short reach parallel optical signal) into another form (such as a long reach serial optical signal) by an interim electrical representation. Coarse and dense wavelength division multiplexing (WDM) are other technologies which are widely used for optically transporting data. Converting between e.g. OSRI and WDM conventionally requires optical-to-electrical-to-optical conversion. In each case, the energy consumed performing such conversion is essentially wasted energy. In addition, the additional circuitry needed to perform electro-optical conversion adds to overall system cost.
Embodiments described herein relate to a system designed to use parallel optics short reach interconnects and map the various channels in an adaptable and predictable manner over different wavelengths. The system can be designed using low-cost parallel-photonic components and extended for longer-reach and reduced fiber count operation. In one embodiment, a given channel number can be mapped to a specific wavelength on the WDM side. Conversion in the optical domain between parallel separate waveguides and channels, and a multiplexing scheme over a single waveguide in the frequency realm is realized. This eliminates the need to perform optical-to-electrical-to-optical conversion between two different optical interconnect technologies e.g. such as OSRI and WDM.
According to an embodiment of an optical adapter, the optical adapter includes an optical coupler, a plurality of fiber optic cables and an optical wavelength conversion device. The optical coupler is operable to receive a plurality of multi-mode single-wavelength optical signals having the same frequency. The plurality of fiber optic cables are arranged in parallel and each have a first end connected to the optical coupler and the other end is coupled to the optical wavelength conversion device. The optical wavelength conversion device is operable to optically convert between the plurality of multi-mode single-wavelength optical signals at the same frequency and a plurality of single-mode optical signals at different frequencies and multiplex the plurality of single-mode optical signals at the different frequencies onto a single-mode multi-wavelength optical waveguide.
According to an embodiment of a method of optical signal conversion, the method includes: optically converting between a plurality of multi-mode single-wavelength optical signals at the same frequency and a plurality of single-mode optical signals at different frequencies; and multiplexing the plurality of single-mode optical signals at the different frequencies onto a single-mode multi-wavelength optical waveguide.
According to an embodiment of a communication system, the communication system includes an electronic circuit, a parallel optical fiber interface, an optical coupler, a plurality of short range fiber optic cables and an optical wavelength conversion device. The electronic circuit is operable to communicate electrical information. The parallel optical fiber interface is electrically coupled to the electronic circuit and operable to convert between the electrical information and a plurality of multi-mode single-wavelength optical signals having the same frequency. The optical coupler is operable to receive the plurality of multi-mode single-wavelength optical signals. The plurality of short range fiber optic cables are coupled at one end to the optical coupler and at the other end to the optical wavelength conversion device, and operable to carry the plurality of multi-mode single-wavelength optical signals. The optical wavelength conversion device is operable to optically convert between the plurality of multi-mode single-wavelength optical signals at the same frequency and a plurality of single-mode optical signals at different frequencies, and to optically multiplex the plurality of single-mode optical signals at the different frequencies onto a single-mode multi-wavelength optical waveguide.
According to an embodiment of an optical adapter at the receive side, the optical adapter includes an optical demultiplexer operable to optically separate an optical signal received over a single-mode multi-wavelength optical waveguide into a plurality of parallel optical signals at different frequencies. The optical adapter further includes a plurality of sets of photodetectors and transimpedance amplifiers operable to receive the parallel optical signals at the different frequencies and convert the parallel optical signals into corresponding electrical signals.
According to an embodiment of a method of processing a received optical signal, the method includes: optically separating an optical signal received over a single-mode multi-wavelength optical waveguide into a plurality of parallel optical signals at different frequencies; and converting the parallel optical signals into corresponding electrical signals.
Those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings.
The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts. The features of the various illustrated embodiments can be combined unless they exclude each other. Embodiments are depicted in the drawings and are detailed in the description which follows.
The optical adapter 120 includes an optical coupler 122 for connecting to the waveguides carrying the parallel MM single-wavelength optical signals from the optical fiber interface 114. The optical adapter 120 also includes an optical wavelength conversion device 124. The optical wavelength conversion device 124 is coupled to the optical coupler 122 via a plurality of short range fiber optic cables 126. One end of each short range fiber optic cable 126 is coupled to the optical coupler 122 and the opposing end is coupled to the wavelength conversion device 124. The short range fiber optic cables 126 carry the MM single-wavelength optical signals between the optical coupler 122 and the optical wavelength conversion device 124. Depending on the technology selected in the wavelength conversion device 124, the optical fibers 126 could also convert the optical signals from MM to single-mode (SM), which is typically the input of a semiconductor optical amplifier (e.g. the SOA 200 shown in
The optical wavelength conversion device 124 optically converts between the MM single-wavelength optical signals at the same frequency (λ1 in
In one embodiment, the optical wavelength conversion device 124 includes an optical wavelength converter 128 associated with each one of the MM single-wavelength optical signals and an optical multiplexer 129. The optical wavelength converters 128 are coupled to respective ones of the short range fiber optic cables 126. Each optical wavelength converter 128 optically converts the frequency of the corresponding MM single-wavelength optical signal to a different frequency so that the MM single-wavelength optical signals are communicated between the wavelength converters 128 and the optical multiplexer 129 at different frequencies and communicated between the wavelength converters 128 and the optical coupler 122 at the same frequency. One of the frequencies (e.g. λ1 in
Under careful selection of the wavelength used in the parallel optics engine of the parallel optical fiber interface 114, a common optical transport component such as a wavelength converter 128 can be used to assign a wavelength to a parallel channel which is pushed out over e.g. a WDM transport with better energy efficiency and system modularity. For example, the optical adapter 120 may be designed for 12 channel parallel optics in the 1550 nm C-band window. On the WDM side, a DWDM (dense WDM) wavelength converter typically converts between 64 wavelengths: λ1, λ2, . . . , λ64. However, in the case of only twelve channels (or in general some number of channels less than 64), the optical wavelength conversion device 124 instead only uses 12 channels (C_1, C_2, . . . , C_12) and assigns each channel a different wavelength or frequency (λ1, λ2, . . . , λ12) as given by C_1->λ1, C_2->λ2, . . . , C_12->λ12. The optical wavelength conversion device 124 then multiplexes the wavelengths over a single waveguide 130 toward the end point which undergoes the reverse operation.
At the receiving end, an optical demultiplexer 132 demultiplexes the optical signal received over the long reach SM multi-wavelength optical waveguide 130 into corresponding recovered ones of the SM optical signals at the different frequencies (C_1, λ1; C_2, λ2; . . . ; C_12, λ12), e.g. as shown in Step 170 of
The optical adapter 120 enables flexible multi-system designs where each system can be interconnected with large bandwidth over long distances. The optical adapter 120 is particularly well-adapted for catastrophe-resilient systems where intra-building redundancy is not sufficient. The optical adapter 120 also reduces cost because only a few separate conversion devices with more expensive WDM components are used. Relatively inexpensive and readily available OSRI technology can be used for the short reach optical connections without increasing cost by embedding WDM into the adapter 120. The optical adapter 120 also saves power by skipping optical-electrical-optical conversion by instead using all-optical wavelength conversion.
The filter output is provided to a 1×2 coupler 204 which splits the filter output in a direction of a tunable coupler 206 and combines or couples optical signals from the tunable coupler 206 in the opposite direction. One optical link between the 1×2 coupler 204 and the tunable coupler 206 includes a phase shifter 208 for shifting the phase of the light signal traversing this path. The other optical link between the 1×2 coupler 204 and the tunable coupler 206 includes a delay loop 210 for delaying the light signal traversing this second path. The tunable coupler 206 is optically coupled to one terminal or port of the optical multiplexer 129.
The wavelength converters 128 associated with the other MM single-wavelength optical signals have a similar architecture, perform a similar wavelength conversion and are coupled to remaining terminals or ports of the optical multiplexer 129. Other types of all-optical wavelength conversion devices may be used to optically convert between short reach MM single-wavelength optical signals and a long reach SM multi-wavelength optical signal.
Terms such as “first”, “second”, and the like, are used to describe various elements, regions, sections, etc. and are not intended to be limiting. Like terms refer to like elements throughout the description.
As used herein, the terms “having”, “containing”, “including”, “comprising” and the like are open ended terms that indicate the presence of stated elements or features, but do not preclude additional elements or features. The articles “a”, “an” and “the” are intended to include the plural as well as the singular, unless the context clearly indicates otherwise.
It is to be understood that the features of the various embodiments described herein may be combined with each other, unless specifically noted otherwise.
Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this invention be limited only by the claims and the equivalents thereof.
