Patent Application
20220269020
The present invention relates to a photoelectric fiber and a communication device and more specifically relates to a photoelectric fiber that includes a photoelectric conversion element at an end portion of a fiber for transmitting an optical signal and a communication device using the photoelectric fiber BACKGROUND
In today's communication, fibers are used in response to a demand for increasing capacity. A communication device used for communication using a fiber has a configuration in which, for example, a digital signal processing unit that performs signal processing and an optical transceiver are connected on the printed circuit board.
In such a communication device, for example, as illustrated in
In the communication device illustrated in
Within the pluggable optical transceiver 1003, a photoelectric conversion element, such as a laser diode (LD) or a photodiode (PD), and a core of the optical fiber 1005 are optically joined. In connecting the photoelectric conversion element and the core of the optical fiber 1005, alignment accuracy within 1 micron or less is necessary in order to reduce optical insertion loss. For this reason, an engagement structure 1006 of a standard connector is often used. This increases the size of the pluggable optical transceiver 1003, relative to the LSI 1001, to a few cm square. Also, to lead the optical fiber 1005 to outside of the printed circuit board 1002, the pluggable optical transceiver 1003 is disposed on the peripheral edge portion of the printed circuit board 1002.
However, the arrangement described above makes the distance connected by the high-frequency electrical wiring 1004 on the printed circuit board 1002 long, causing degradation of the electrical signals. In order to compensate for the deterioration, a circuit chip for performing waveform correction processing, such as reshaping, retiming, and regenerating, can be provided. However, when a waveform correction circuit chip is provided, the size of the LSI 1001 and the pluggable optical transceiver 1003 is made even larger. As a result, there is a problem in that the number of pluggable optical transceivers that can be connected to one LSI is limited, and the transmission capacity of the entire the communication device also reaches the limit.
Embodiments of the present invention are directed at reducing the size of an optical transceiver.
To achieve the object described above, a photoelectric fiber (100) according to embodiments of the present invention includes:
a fiber (1i) including a core (102) through which light is guided;
an electrical unit (11o) formed continuously with the fiber, the electrical unit being configured to house a photoelectric conversion chip (113) including a photoelectric conversion element; and
an external electrode (111) formed on a front surface of at least one of the fiber or the electrical unit, wherein
the photoelectric conversion chip (113) is optically connected to the core and electrically connected to the external electrode.
According to embodiments of the present invention, the photoelectric conversion element is provided at the end portion of the fiber, so it is possible to reduce the size of a transceiver that converts electrical signals into optical signals or converts optical signals received from the fiber into electrical signals. By reducing the size, the transceiver can be disposed in the vicinity of the LSI. Thus, high-frequency electrical signal wiring can be shortened and signal degradation can be prevented. Moreover, since a plurality can be arranged in parallel, it is possible to advantageously increase the transmission capacity of the entire communication device.
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The configuration of a photoelectric fiber according to the first embodiment of the present invention is illustrated in
A photoelectric fiber 100 according to the present embodiment includes a fiber 101 including a core 102 in which light is guided, an electrical unit 110 formed continuously with the fiber 101, and an external electrode 11 formed on the front surface of the electrical unit 110.
Of these, the electrical unit 110 includes a photoelectric conversion chip (hereinafter referred to simply as “chip”) 113 including a photoelectric conversion element, wiring 114 connecting the chip 113 and the external electrode 111, and a filling unit 117 that houses the chip 113 and the wiring 114.
In the present embodiment, in the chip 113, a photoelectric conversion element (not illustrated), such as a photodiode that converts an optical signal into an electrical signal or a laser diode that converts an electrical signal into an optical signal, and a drive circuit are formed. An electrode pad (hereinafter simply referred to as “pad”) 116 that electrically connects to the external electrode in is formed on the top surface of the chip 113 formed in a rectangular parallelepiped shape. Regarding the number of pads, for example, if there are four terminals, two terminals are used for the electrical differential signal input and output from the external circuit and the remaining two terminals are used for the power supply and the ground, thus enabling power supply and signal processing. In a case where the chip 113 is formed from silicon and the power supply circuit is mixed, one power supply input may be converted to a plurality of potentials and used.
Furthermore, an end surface (hereinafter referred to as “optical input/output unit”) 115 of the optical waveguide serving as the input/output unit of the optical signals to the chip 113 is provided on the side surface of the chip 113.
Hereinafter, the chip 113 and the wiring 114 may be collectively referred to as a photoelectric conversion unit 112.
As illustrated in
The above-described electrical unit 110 is provided at the end portion of the fiber 101 so as to be coaxial with the fiber 101. In this state, the core 102 of the fiber 101 and the optical input/output unit 115 of the chip 113 are aligned, and the core 102 of the fiber 101 is optically connected.
For example, the fiber 101 is a fiber with an outer diameter of 125 um including the cladding, and the electrical unit 110 also has a cylindrical shape with an outer diameter of approximately 125 um and a length of approximately 500 um. The chip 113 has a shape of 0.1 mm×0.3 mm×30 umt, and on the chip 113, four 30 um square pads 116 are disposed at a 50 um pitch. The chip 113 is, for example, a silicon photonics circuit, and is provided with PD using germanium or an LD in which a compound semiconductor adhered to a silicon substrate emits light. The wiring 114 is part of a bonding wire using gold. To make the cylindrical electrical unit 110 containing these, the filling unit 117 made of a resin fills the space.
The external electrode 11 is made of metal and is formed in an annular shape on the circumferential surface of the cylindrical electrical unit 11o. The external electrode in is connected to the pad 116 of the chip 113 by the wiring 114. In the present embodiment, four external electrodes in for a power supply ground (GND), two differential signal terminals (S), and a power supply (V) are provided corresponding to the photoelectric conversion element formed on the chip 113 and the drive circuit thereof.
Operation and Use Example of Photoelectric Fiber
In the photoelectric fiber 100, light incident from the core 102 enters into a photoelectric conversion device, such as a photo detector, PD, or the like, from the optical input/output unit 115 of the chip 113 is output from the pad 116 as an electrical signal. Since the pad 116 is connected to the external electrode 111 via the wiring 114, the photoelectric-converted electrical signal can be led out via the external electrode 111.
Similarly, the electrical signals input from the external electrode in are output from the chip 113 as optical signals by a photoelectric conversion device (laser diode, LD) in the chip 113 and guided through the core 102 of the fiber 101.
The communication device includes the printed circuit board 150, a communication LSI 151 mounted on the printed circuit board 150, a printed circuit board electrode 160 formed on the printed circuit board 150 and wiring (not illustrated) for connecting the printed circuit board electrode 160 and the communication LSI 151, and the photoelectric fiber 100 connected to the electrode 160 and electrically connected to the communication LSI 151 via wiring. Note that the printed circuit board electrode 160 is connected to the input/output terminals for the electrical signal of the communication LSI 151 and is connected to a power supply supplied from the other portion of the printed circuit board 150.
As shown in
Here, the LSI 151 is, for example, a 20 mm square Ball Grid Array (BGA) package, and the solder balls 152 are formed, for example, into 0.45 mm spheres. When the external diameter of the photoelectric fiber 100 is approximately 125 um, in particular, the electrical unit 11o of the photoelectric fiber 100 is smaller than the LSI 151, so it is possible to dispose the photoelectric fiber 100 in the vicinity of the LSI, for example, within 1 mm.
By disposing the photoelectric fiber 100 in the vicinity of the LSI 151 in this manner, the wiring connecting the photoelectric fiber 100 and LSI 151 can be shortened and, as a result, degradation of the electrical signal can be suppressed.
As illustrated in
When mounted on the printed circuit board 150, the external electrode 111 of the photoelectric fiber 100 may simply be electrically connected to the printed circuit board electrode 160, so the alignment accuracy is sufficiently approximately 10 um, and the mounting process is simplified.
Manufacturing Method
Next, a method of manufacturing the photoelectric fiber 100 according to the present embodiment will be described with reference to
First, a normal Au wire is subjected to ultrasonic crimping using a wire bonding device on the pad 116 of the chip 113 to form a stud bump 201, and the wires are cut at a suitable length (
Next, the optical input/output unit 115 provided on the side surface (chip end surface) of the chip 113 is optically aligned and connected with the core 102 (
Next, a cylindrical container 217 containing the resin that forms the filling unit 117 is prepared, and the chip 113 connected to the end surface of the fiber and the stud bumps 201 are immersed in the cylindrical container 217, and the resin is cured by heat or the like (
After curing the resin, the outer diameter is cut and polished by a small lathe to form the filling unit 117 into a clean cylindrical shape (
Note that by configuring the external electrode 111 to have a circumferential shape, the vapor deposition process of
When the optical signal that is guided through the core 102 is a high-speed signal of 100 Gbps, for example, the electrical signal converted by the chip 113 is a high-frequency signal of approximately 100 GHz. The higher the frequency of the electrical signal, the higher the transmission loss in the electrical wiring, causing more signal deterioration or interference between adjacent wiring. Thus, it is necessary that the electrical wiring be made as short as possible.
In the structure illustrated in
In known techniques, the chip is connected to the outside using a bonding wire or bumps for a flip-chip connection from the pads 116 of the chip 113, but in such a connection, the plane of the chip 113 and the plane of the external printed circuit board are connected, and the distance must also be made long. In contrast, in the photoelectric fiber 100 of the present embodiment, the electrode 11 is a three-dimensional electrode corresponding to the cylindrical shape of the fiber 101, and the chip 113 is disposed on the inside of the three-dimensional electrode, allowing for minimal electrical wiring. As a result, there is no deterioration of the electrical signal due to loss or interference, and high-speed signals can be transmitted.
In addition, in the present embodiment, the chip 113 is housed within the cylindrical electrical unit 11o having the same outer diameter as the outer diameter of the fiber 101, and only the external electrode in is placed outside of the fiber 101 and the electrical unit 110. Accordingly, the photoelectric fiber 100 can be made smaller to a size similar to that of the fiber 101, micro alignment of the optical component is not necessary, and the photoelectric fiber 100 can be used for rough alignment of an electrical components. These advantages can be obtained.
In the photoelectric fiber 100 described above, when the length of the cylindrical electrical unit 11o is extended along the axis thereof, a plurality of chips 113 can be disposed within the electrical unit 11o, and more pads and electrodes can be provided.
In addition, naturally, the fiber 101 can be used as a multi-core fiber, can be used for both transmission and reception using a plurality of cores, and can transmit in parallel using multiple cores of one fiber to increase capacity.
Also, as illustrated in
Next, a photoelectric fiber according to the second embodiment of the present invention will be described with reference to
In the photoelectric fiber 100 according to the first embodiment, as illustrated in
In this example, as illustrated in
Furthermore, as illustrated in
According to the present embodiment, because the chip 413 is supported by the terrace 401, the strength of the structure can be increased compared to the structure of the photoelectric fiber according to the first embodiment.
Next, the third embodiment of the present invention will be described with reference to
In the first embodiment described above, as illustrated in
For example, as illustrated in
The photoelectric fiber according to the present embodiment employs the chip 513 described above. For example, in a case where the chip 513 is a rear surface incident type photodetector, light is incident from the rear surface side on the opposite side to the pad 516, expands and is received by the optical input/output unit 515 on the front surface. With the light receiving unit and the core 102 of the fiber 101 in optical alignment, as illustrated in
Although not illustrated, in the description of the first embodiment, in the same steps as described with reference to
According to the present embodiment, by such way, the photoelectric fiber 100 can be realized regardless of the surface relationship between the optical input/output unit and the pad.
Next, a photoelectric fiber according to the fourth embodiment of the present invention will be described with reference to
In the photoelectric fiber 100 according to the first embodiment described above, as illustrated in
With the photoelectric fiber according to the present embodiment, it is expected that, as illustrated in
In the present embodiment, the external electrode 611 is the same as in the first embodiment in that it is a circular shape, but in the first embodiment, the external electrode 111 is formed on the front surface of the electrical unit 11o, and in the present embodiment, the external electrode 611 is formed on the front surface of the fiber 101. As illustrated in
Furthermore, as illustrated in
After forming the pad 616, the wiring 614, and the external electrode 611, as illustrated in
In the present embodiment, the external electrode 611 is formed to be in contact the front surface of the fiber 101, and thus, the external electrode 611 can be formed before the chip 513 is mounted on the fiber 101. Thus, compared to the first embodiment described above in which the process of forming the external electrode 11 takes place after optical connection between the core 102 of the fiber 101 and the chip 113, the present embodiment has an advantage in that the external electrode 611 can be formed prior to mounting the chip 513 to reduce the load from the process after the core 102 of the fiber 101 and the chip 513 are optically connected.
Next, a photoelectric fiber according to the fifth embodiment of the present invention will be described with reference to
In the fourth embodiment described above, the wiring 614 is formed on the front surface of the fiber 101, while in the present embodiment, as illustrated in
The electrode structure as described above can be obtained using a hole structure fiber 101a as illustrated in
First, the hole structure fiber 101a is prepared. The hole structure fiber 101a includes, in addition to the core 102, a plurality of horizontal holes 701 (four in
Next, in the fiber 101a, a plurality of vertical holes 702 (four in
After the vertical holes 702 are formed, an electrode (circumferential electrode) is formed on the side surface of the fiber 101a in the circumferential direction. Such a circumferential electrode can be formed, for example, by forming a resist pattern on the side surface of the fiber 101a and performing vapor deposition with an Au mask and an Ni base. The circumferential electrode is formed including four opening portions for the four vertical holes 702. As a result, a total number of four circumferential electrodes are formed in a striped shape on the side surface of the fiber 101a.
Next, the end of the fiber 101a is turned downward and immersed in the molten solder to fill the openings of the horizontal holes 701, and the air pressure is reduced while the vertical holes 702 are open. Then, the inside of the horizontal holes 701 are filled with solder, and reducing the air pressure is stopped in a state where the solder flows out of the vertical holes 702 that opens to the side surface of the fiber 101a, and the temperature is lowered to room temperature by pulling the fiber 101a up from the molten solder. At this time, because solder has high wettability with Au and poor wettability with glass base, some of the solder overflowing from the vertical holes 702 spreads over the Au of the circumferential electrode described above, while the solder does not attach to the front surface of the cladding of the fiber 101a where the circumferential electrode is not formed. In this manner, the external electrode 11, which is selectively formed in correspondence with the circumferential electrode, and the internal wiring 714 connected to the external electrode 11 through the horizontal holes 701 and the vertical holes 702 are formed.
Thereafter, when mounting the chip 513 as illustrated in
As described above, because the internal wiring 714 is formed through the interior of the fiber 101a, the external electrode 111 can be formed before the chip is mounted. Accordingly, as in the fourth embodiment, the load caused by the process after the optical connection of the core 102 of the fiber 101a and the chip 513 can be reduced. Moreover, because the wiring passes through the interior of the fiber 101a, the wiring and the external electrode cause no undulation and the outer diameter of the fiber 101a can be formed closer to that of a perfect circle.
Note that in the first to fifth embodiments described above, an example has been described in which the filling unit which constitutes the electrical unit together with the chip is formed into a cylindrical shape and has approximately the same diameter as the fiber. However, the filling unit does not need to necessarily be cylindrical and may be, for example, formed into a prismatic shape. Furthermore, the filling unit does not need to necessarily have the same diameter as the fiber and may be formed thicker than the fiber, for example. Also, as long as the external electrode can be formed on the front surface of the filling unit or the fiber and can connect to the outside, an aspect in which the end portion of the fiber is installed inside the filling unit together with the chip is also included in forming the electrical unit continuously with the fiber.
Embodiments of the present invention can be used in the field of optical communication, optical sensing, and other processes involving transmission of optical signals and photoelectric conversion.
This application is a national phase entry of PCT Application No. PCT/JP2019/028298, filed on Jul. 18, 2019, which application is hereby incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/028298 | 7/18/2019 | WO |
