Optical communication system

Abstract

Provided is an optical communication system comprising: a multicore fiber that is made of plastic and that is provided with a plurality of cores which have a GI-type refractive index distribution in cross-section; a light source that is provided with a plurality of light-emitting elements which are arranged in an array; and a light receiver that is provided with a plurality of light-receiving elements which are arranged in an array, wherein the arrangement pattern of the plurality of cores in the multicore fiber at least partially corresponds to the arrangement pattern of the plurality of light-emitting elements in the light source and / or the arrangement pattern of the plurality of light-receiving elements in the light receiver, and at least some of the plurality of cores and at least some of the plurality of light-emitting elements and / or the plurality of light-receiving elements are collectively optically coupled.

Description

Optical communication system

[0001] This invention relates to an optical communication system.

[0002] With the explosive increase in information traffic in data centers and other similar environments, expanding the transmission capacity of optical interconnects has become a critical issue. To address this challenge, in addition to improving the communication speed per lane, multi-lane (multi-core) configuration, which involves parallelizing numerous optical fibers, is an essential element.

[0003] To increase the number of cores, ribbon fibers, which are optical fibers arranged in a one-dimensional manner, are commonly used. In ribbon fibers, the fiber pitch (the distance between two optical fibers) is generally 250 μm. To further increase transmission capacity, it is necessary to reduce the fiber pitch to less than 250 μm or to use a higher density multi-core arrangement, such as a two-dimensional arrangement of optical fibers.

[0004] Meanwhile, in terms of light sources, technologies have been developed to arrange vertical-cavity surface-emitting lasers (VCSELs) and micro-LEDs in high-density arrays (one-dimensional or two-dimensional). There is a strong demand for multi-core optical fiber transmission lines that can efficiently couple with such high-density light source arrays.

[0005] When aiming for high density using glass optical fibers, a ribbon-forming process is essential, which involves precisely aligning and bundling multiple single-core fibers one by one. However, this ribbon-forming process is extremely complex and costly, especially when implementing ultra-high density, such as when reducing the pitch or arranging optical fibers in a two-dimensional configuration. While glass multi-core fibers exist as a technology that eliminates the need for such a ribbon-forming process, they require complex preform fabrication processes such as lamination and drilling, making low-cost mass production extremely difficult.

[0006] On the other hand, there are plastic optical fibers (POFs) that can be formed in a single batch by extrusion molding and have excellent manufacturing costs (Non-Patent Literature 1).

[0007] Chikafumi Tanaka, Kazuyoshi Kurashima, Masaki Naritomi, Atsushi Kondo, and Yasuhiro Koike, “The First Low-Loss and High-Bandwidth 61- 127 Channel Graded-Index Steric Cores Polymer Waveguide”, OWG6, OFC / NFOEC 2008.

[0008] However, there are no reports on high-density and high-speed transmission characteristics using plastic multi-core fibers, and there is room for improvement in optical communication systems that achieve low-cost yet broadband transmission.

[0009] The present invention has been made in view of the above, and aims to provide an optical communication system that achieves low cost while achieving high bandwidth transmission.

[0010] To solve the above-mentioned problems and achieve the objective, one aspect of the present invention is an optical communication system comprising: a multicore fiber made of plastic having a plurality of cores having a GI-type refractive index distribution in its cross-section; a light source having a plurality of light-emitting elements arranged in an array; and a photodetector having a plurality of photodetectors arranged in an array, wherein the arrangement pattern of the plurality of cores in the multicore fiber corresponds at least partially to at least one of the arrangement pattern of the plurality of light-emitting elements in the light source and the arrangement pattern of the plurality of photodetectors in the photodetector, and at least a portion of the plurality of cores and at least a portion of at least one of the plurality of light-emitting elements and the plurality of photodetectors are optically coupled together as a whole.

[0011] According to the present invention, low-cost, high-bandwidth transmission can be achieved.

[0012] Figure 1 is a schematic configuration diagram of an optical communication system according to an embodiment. Figure 2 is a schematic cross-sectional view of a multicore fiber. Figure 3 is a diagram showing the arrangement of light-emitting elements in a light source. Figure 4 is a diagram showing the arrangement of photodetectors in a photodetector. Figure 5 is a diagram showing an example of BER characteristics. Figure 6 is a diagram showing an example of an eye diagram. Figure 7 is a diagram showing the light intensity distribution when an optical signal is input to the core of CH3. Figure 8 is a diagram showing the light intensity distribution when an optical signal is input to the core of CH5. Figure 9 is a diagram showing the light intensity distribution when an optical signal is input to the core of CH7. Figure 10 is a diagram showing the inter-core crosstalk estimated from the light intensity distributions including Figures 7 to 9.

[0013] Embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to these embodiments. Furthermore, in each drawing, the same or corresponding elements are denoted by the same reference numerals as appropriate, and redundant explanations are omitted as appropriate. It should also be noted that the drawings are schematic, and the dimensional relationships of each element may differ from those in reality. Even between drawings, there may be parts where the dimensional relationships and ratios differ.

[0014] <Embodiment> Figure 1 is a schematic diagram of an optical communication system according to an embodiment. The optical communication system 1000 is a system for performing optical communication between two servers S. The optical communication system 1000 comprises a server S, a multicore fiber 100 which is an optical transmission path, and two optical transceivers 200 connected to the multicore fiber 100. In this specification, "server S" is a general term for communication equipment and is not limited to servers, but may include switches, etc.

[0015] (Structure of a multicore fiber) Figure 2 is a schematic cross-sectional view of a multicore fiber. The multicore fiber 100 comprises a plurality of cores 101 arranged in the cross-section and a cladding 102 surrounding the cores, and is made of plastic. In addition to the cores 101 and cladding 102, the multicore fiber 100 may further include one or more overcladding layers (protective layers), doublecladding layers, or other arbitrary layers as needed, and these layers are also made of plastic.

[0016] The cores 101 are arranged in a two-dimensional and concentric manner. Alternatively, they can be described as being arranged in a grid. In this embodiment, there are 61 cores 101. Furthermore, the cores 101 have a Graded Index (GI) type refractive index distribution. In this specification, in the case of a core arrangement such as that of a multicore fiber 100, the nine cores arranged in a horizontal row are sometimes identified by assigning channel numbers CH1 to CH9. Figure 2 shows the positions of CH1, 5, and 9.

[0017] Such a multicore fiber 100 can be formed integrally, for example, by a single extrusion molding process. Specifically, molten core material and cladding material are simultaneously extruded from a die having an outlet shaped to correspond to the desired core arrangement. If the multicore fiber 100 includes layers other than the core 101 and cladding 102, the plastics corresponding to each of these layers may also be extruded simultaneously. Subsequently, a thermal diffusion process is performed to thermally diffuse the dopant, thereby producing a multicore fiber in which multiple cores having a GI-type refractive index distribution are formed in the desired arrangement. This manufacturing method eliminates the need for complex preform fabrication and ribbon formation processes that were essential in the production of glass fibers, resulting in a significant simplification and cost reduction of manufacturing.

[0018] The multicore fiber 100 may be made of a plastic that is transparent in the wavelength range of the light source used, for example, a fully fluorinated resin material or a partially fluorinated resin material.

[0019] As for all-fluorine resin materials, products such as TEFRON-AF (DuPont), HyflonAD (Solvay), and CYTOP (Asahi Glass Co., Ltd.) can generally be used. Alternatively, all-fluorine polymers copolymerized with tetrafluoroethylene or the like in the main ring structure of these materials may be used. All-fluorine polymers having a dioxolene skeleton can also be used.

[0020] As partially fluorinated resin materials, polymers of acrylic monomers such as HFIP 2-FA and TFEMA, or polymers in which hydrogen atoms in the benzene ring are substituted with fluorine, can be used.

[0021] Furthermore, examples of dopants added to the core to form a GI-type refractive index distribution include oligomers of CTFE (chlorotrifluoroethylene). Other examples include low molecular weight compounds or compounds in which hydrogen atoms present in these compounds are replaced with fluorine atoms. Examples of low molecular weight compounds with high refractive indices include diphenyl sulfone (DPSO) and diphenyl sulfone derivatives (e.g., chlorinated diphenyl sulfones such as 4,4'-dichlorodiphenyl sulfone and 3,3',4,4'-tetrachlorodiphenyl sulfone), sulfur compounds such as diphenyl sulfide (DPS), diphenyl sulfoxide, dibenzothiophene, and dithiane derivatives; phosphoric acid compounds such as triphenyl phosphate (TPP) and tricresyl phosphate; benzyl benzoate; benzyl n-butyl phthalate; diphenyl phthalate; biphenyl; and diphenylmethane. Compounds in which some of the hydrogen atoms in these low molecular weight compounds are replaced with fluorine are also candidates. These may be used individually or in combination of two or more.

[0022] Furthermore, the refractive index distribution coefficient is a parameter used to specify the refractive index distribution of a GI type. The refractive index distribution is expressed using the refractive index distribution coefficient as shown in the following equation. Here, n １ n is the refractive index at the center of the core, ２n(r) is the refractive index of the cladding, Δ is the relative refractive index difference between the refractive index of the cladding and the refractive index of the core at the center, g is the refractive index distribution coefficient (also called the g-value), r is the radial distance from the center of the core, a is the radius of the core, and n(r) is the refractive index of the core at distance r. n(r) = n １ [1 - 2Δ(r / a)] ｇ ] １／２ 0 ≤ r ≤ a n ２ r>a

[0023] In the multi-core fiber 100, the refractive index distribution coefficient is preferably set to a value that suppresses modal dispersion. The optimal refractive index distribution coefficient g is determined by the wavelength dependence of the refractive index of the material constituting the core 101 and the operating wavelength, but the maximum transmission bandwidth is generally obtained when g ≈ 2.00. The design range of g depends on the transmission rate in the target application, the length of the multi-core fiber 100, and the spectral width of the optical signal, but in practice, a sufficient transmission bandwidth can be obtained if it is within the range of 1.50 to 3.00. The range of g is more preferably 1.70 to 2.50, even more preferably 1.70 to 2.30, and particularly preferably 1.95 to 2.20. Furthermore, when used in combination with VCSEL, it is preferable that each core operates in multimode, and according to standard multimode optical fibers, the core diameter is preferably about 50 μm and the numerical aperture (NA) is preferably about 0.20. For further density improvement, the core diameter may be made smaller, for example, to 25 μm or less. In addition, to satisfy the single-mode condition at a predetermined operating wavelength, it is possible to set the core diameter to, for example, 10 μm or less. Furthermore, the numerical aperture (NA) can be designed considering the divergence angle of the light source, and may be set to, for example, 0.30 or less, 0.20 or less, 0.15 or less, or 0.12 or less.

[0024] (Configuration of the optical transceiver) The optical transceiver 200 comprises a light source 210, a photodetector 220, an optical coupling unit 230, a driver 240, a transimpedance amplifier (TIA) 250, and a digital signal processor (DSP) 260.

[0025] The light source 210 comprises 61 light-emitting elements 211 arranged in an array. Each light-emitting element 211 outputs an optical signal. Figure 3 shows the arrangement of the light-emitting elements 211 in the light source 210. As shown in Figure 3, the arrangement pattern of the light-emitting elements 211 in the light source 210 corresponds to the arrangement pattern of the cores 101 in the multicore fiber 100. The light-emitting elements 211 are, for example, VCSELs or microLEDs. Therefore, the light source 210 includes a VCSEL array or a microLED array.

[0026] The photodetector 220 comprises 61 photodetectors 221 arranged in an array. Each photodetector 221 receives an optical signal and outputs a current signal corresponding to the received light intensity. Figure 4 shows the arrangement of the photodetectors 221 in the photodetector 220. As shown in Figure 4, the arrangement pattern of the photodetectors 221 in the photodetector 220 corresponds to the arrangement pattern of the cores 101 in the multicore fiber 100. The photodetectors 221 are, for example, photodiodes.

[0027] The optical coupling unit 230 is configured to optically couple the light-emitting element 211 to the corresponding core 101. The optical coupling unit 230 is also configured to optically couple the light-receiving element 221 to the corresponding core 101. As a result, multiple cores 101, multiple light-emitting elements 211, and multiple light-receiving elements 221 are optically coupled together. The optical coupling unit 230 may consist of a spatial coupling system including, for example, mirrors or lenses.

[0028] The optical signal output from the light-emitting element 211 of one optical transceiver 200 is transmitted through the core 101 of the multicore fiber 100 and received by the light-receiving element 221 of the other optical transceiver 200.

[0029] The driver 240 drives the light source 210. Specifically, the driver 240 drives the light source 210 to output an optical signal that includes a modulation signal provided by the server S.

[0030] The TIA250 converts the current signal output from the photodetector 221 into a voltage signal and outputs it.

[0031] The DSP 260 preprocesses the modulation signal given from the server S to the driver 240, or postprocesses the voltage signal output from the TIA 250 and outputs it to the server S.

[0032] In the optical communication system 1000 configured as described above, since the multi-core fiber 100 having a core with a GI-type refractive index distribution is used as a transmission path, wideband transmission can be realized at a low cost.

[0033] Further, in the optical communication system 1000, since the arrangement pattern of the light emitting element 211 corresponds to the arrangement pattern of the core 101, and the arrangement pattern of the light receiving element 221 corresponds to the arrangement pattern of the core 101, batch alignment and connection of the multi-core fiber 100, the light source 210, and the light receiver 220 are easily possible, and the mounting density of the entire system is dramatically improved.

[0034] (Examples of transmission rate and modulation method) The transmission rate per lane (one core) can be appropriately selected according to the type of the light emitting element 211 and the modulation method of the modulation signal. For example, when the light emitting element 211 is a VCSEL, as the transmission rate, 10 Gbit / s, 25 Gbit / s, 32 Gbit / s, 50 Gbit / s, 64 Gbit / s, 100 Gbit / s, 128 Gbit / s have been put into practical use, and further expansion to 200 Gbit / s is also expected. As the modulation method, NRZ (Non-Return-to-Zero) and PAM (Pulse Amplitude Modulation) 4 are common, but PAM4 is mostly used at high speeds of 50 Gbit / s or more.

[0035] On the other hand, when the light emitting element 211 is a micro LED, as the transmission rate, 1 Gbit / s, 2 Gbit / s, 4 Gbit / s, 5 Gbit / s, 10 Gbit / s, 15 Gbit / s, etc. are assumed. As the modulation method, NRZ is common.

[0036] (Example of bandwidth density) As an index of the performance of the optical communication system 1000, the bandwidth density per unit cross-sectional area of the optical fiber (Gbit / s / mm ２will be described. In the case of existing technologies where the fiber pitch is 250 μm, assuming that 16 cores (4 × 4) can be arranged per millimeter ２ and the transmission rate per lane is 25 Gbit / s, the bandwidth density is 400 Gbit / s / mm ２ . Also, when the transmission rate per lane is 50 Gbit / s, the bandwidth density is 800 Gbit / s / mm ２ , and when it is 100 Gbit / s, the bandwidth density is 1.6 Tbit / s / mm ２ .

[0037] In contrast, in the case of the multi-core fiber 100, the arrangement interval (core pitch) between the two cores 101 is 250 μm or less, for example, 35 μm. As a result, a bandwidth density of 400 Gbit / s / mm ２ or more can be easily achieved, and furthermore, a bandwidth density of 800 Gbit / s / mm ２ or more and 1.6 Tbit / s / mm ２ or more can also be easily achieved. Also, the number of the core portions per preferred unit cross-sectional area is 16 / mm ２ or more, more preferably 64 / mm ２ or more, and even more preferably 256 / mm ２ .

[0038] (Example of Bandwidth-Distance Product) In an optical fiber with a step-index (SI) type refractive index distribution, there is a problem that due to mode dispersion, the transmission rate that can be transmitted decreases significantly as the transmission distance increases. As a result, there is also a limit to the product of the transmission rate and the transmission distance (bandwidth-distance product), which is a performance index of a single core.

[0039] In contrast, in the multi-core fiber 100, since the refractive index distribution of the core 101 is of the GI type, mode dispersion can be significantly suppressed. As a result, high-rate transmission over a long distance can be maintained.

[0040] Furthermore, if the core 101 is made of an all-fluoropolymer material, material dispersion is also reduced, resulting in a significant improvement in bandwidth. As a result, the bandwidth-to-distance product in a single core 101 can be 450 Gbps·m or more. Moreover, if the transmission rate is 53.125 Gbps and the transmission distance is 10 m, the bandwidth-to-distance product can be 500 Gbps·m or more. Furthermore, if the transmission rate is 53.125 Gbps and the transmission distance is 30 m, the bandwidth-to-distance product can be 1.5 Tbps·m or more.

[0041] (Energy Efficiency) Increasing the capacity of optical interconnects is achieved through two axes: improving the transmission rate (R) per lane and increasing the number of cores (N). Conventionally, improving R has been achieved by combining multi-level modulation (e.g., PAM4) and signal compensation by DSP. However, processing by DSP generally increases power consumption and latency, resulting in a deterioration of energy consumption per bit (J / bit).

[0042] On the other hand, in the optical communication system 1000, since N in the multicore fiber 100 is extremely large, R may be set to a level that reduces the load on the DSP 260 or allows it to be omitted altogether, thereby ensuring the necessary total transmission capacity T = N × R. This reduces the power consumption of the DSP 260 and reduces the overall energy consumption of the system.

[0043] For example, it is preferable that the transmission rate in one core 101 is set such that the energy consumption per unit bit is 20 pJ / bit or less. For example, if the power consumption of the optical transceiver 200 is 16 W and the transmission rate is 800 Gbit / s, the energy consumption per unit bit will be 20 pJ / bit. It is even more preferable that the energy consumption per unit bit be 10 pJ / bit or less, and it may also be 5 pJ / bit or less or 1 pJ / bit or less.

[0044] (Experimental Example) A multicore fiber with 61 cores in the configuration shown in Figure 2 was fabricated using an all-fluorine resin material. The transmission characteristics were then measured using nine cores arranged in a horizontal row in the multicore fiber. The diameter and numerical aperture of each core were approximately 25 μm and 0.18, respectively. The attenuation and bandwidth of each core were approximately 0.045 dB / m and 750 GHz·m, respectively.

[0045] As the light-emitting element, a VCSEL with a modulation bandwidth of approximately 22 GHz and a laser oscillation wavelength in the 850 nm band was used. The VCSEL was directly modulated by applying a PAM4 signal generated by a pulse pattern generator via a bias T. A 7-tap feedforward equalizer was also applied to the pulse pattern generator. The optical signal from the VCSEL was coupled to the core of a multicore fiber using an aspherical lens.

[0046] The photodetector was a photodiode connected to an integrated circuit containing a TIA and a clock data recovery (CDR) circuit. The optical signal transmitted through the core was focused into the effective area of ​​the photodetector using a collimating lens and a focusing lens.

[0047] The bit error rate (BER) was measured using a BER tester (Keysight M8050A), and the eye diagram was measured using a sampling oscilloscope (Keysight N1092C).

[0048] Figure 5 shows an example of BER characteristics. The length of the multicore fiber is 10 m. The transmission rate is 53.125 Gb / s, and the signal pattern is 2 ３１ A pseudo-random bit sequence (PRBS) of -1 was used. Error code correction (FEC) was not used in any of the cores CH1 to CH9. －１２ A BER characteristic of less than 5 was achieved.

[0049] The graph in Figure 5 shows the dependence of BER on the received optical power. This graph is generally called the BER curve and is used to determine the reception conditions (required received optical power) necessary to achieve a predetermined BER. For example, in Figure 5, BER = 10 －１２To achieve this, a received optical power of approximately -4 dBm is required. The smaller the variation in the required received optical power in each channel (core), the higher the uniformity of the transmission characteristics between cores. The variation in received optical power (difference between the maximum and minimum values) required to achieve a predetermined BER is preferably 3 dB or less, more preferably 2 dB or less, and even more preferably 1 dB or less.

[0050] Figure 6 shows an example of an eye diagram. Note that Figure 6 shows the eye diagram for CH5. The transmission distance (length of the multicore fiber) was 2m, 10m, or 30m. The transmission rate was 53.125 Gb / s or 106.25 Gb / s. The test pattern was SSPRQ (Short Stress Pattern Random Quaternary). The extinction ratio (ER) was adjusted to approximately 3.0 dB for 53.125 Gb / s and approximately 2.5 dB for 106.25 Gb / s, in accordance with IEEE standards.

[0051] As shown in Figure 6, a sufficiently open eye diagram was obtained for all transmission rates and distances. The TDECQ (Transmitter and Dispersion Eye Closure Quaternary) value is also shown in the figure. TDECQ is an index for quantitatively evaluating the waveform quality of the PAM4 signal, and is a parameter that expresses the degree of eye closure in dB compared to an ideal waveform. The smaller the TDECQ value, the less noise and distortion there is, and the better the signal quality. In the case shown in Figure 6, at a transmission rate of 53.125 Gb / s, the TDECQ was 0.25 dB at a transmission distance of 2 m, 0.36 dB at 10 m, and 0.49 dB at 30 m, and the degradation of TDECQ at 30 m compared to 2 m was 0.24 dB. On the other hand, at a transmission rate of 106.25 Gb / s, the TDECQ degradation was 2.96 dB at a transmission distance of 2 m, 3.02 dB at 10 m, and 3.52 dB at 30 m, with the TDECQ degradation at 30 m being 0.56 dB compared to 2 m. It is preferable that the TDECQ degradation associated with transmission be 3 dB or less, more preferably 2 dB or less, and more preferably 1 dB or less. In Figure 6, even at a transmission distance of 30 m, the TDECQ was less than 4.4 dB, which is the value required by the IEEE standard.

[0052] Next, we evaluated the inter-core crosstalk in the CH1-9 cores of the fabricated multicore fiber. Specifically, we used a VCSEL with a laser oscillation wavelength in the 850 nm band to input an optical signal to one of the CH1-9 cores, and the output optical signal was received by a single-mode optical fiber. At this time, the optical intensity distribution along the axis was measured by scanning the single-mode optical fiber along the axis in which the CH1-9 cores were arranged. The length of the multicore fiber was 2 m or 30 m. In addition, the multicore fiber was wound on an 8-inch diameter spool to avoid significant bending. Furthermore, the measurements were performed in a darkroom to minimize measurement noise.

[0053] Figures 7, 8, and 9 show the light intensity distribution when an optical signal is input to the CH3, CH5, and CH7 cores, respectively. The horizontal axis represents the radial position, and the vertical axis represents the light intensity normalized by the light intensity measured at the position of the core to which the optical signal was input.

[0054] The results shown in Figures 7-9 suggest that the inter-core crosstalk between the core receiving the optical signal and the adjacent core is less than -30 dB. Furthermore, since no significant difference was observed in the optical intensity distribution profiles for 2 m and 30 m, it was confirmed that the inter-core power transitions, where light transitions between cores while the optical signal propagates through the core, are extremely small.

[0055] Figure 10 shows the inter-core crosstalk estimated from the light intensity distribution including Figures 7-9. As shown in Figure 10, the fabricated multi-core fiber showed little variation in inter-core crosstalk, confirming that the core characteristics were extremely uniform. Specifically, the inter-core crosstalk was -30 dB or less for all of the CH1-9 cores. Furthermore, Figure 10 confirms that the increase in inter-core crosstalk was extremely small even when the length of the multi-core fiber increased from 2 m to 30 m. Specifically, the average value of the inter-core crosstalk of the CH1-9 cores at a length of 2 m was -34.9 dB, while the average value at a length of 30 m was -34.2 dB, an increase of only 0.7 dB.

[0056] In the above embodiment, the arrangement pattern of the light-emitting element 211 corresponds to the arrangement pattern of the core 101, and the arrangement pattern of the light-receiving element 221 corresponds to the arrangement pattern of the core 101. However, the arrangement pattern of the core may at least partially correspond to either the arrangement pattern of the light-emitting element or the arrangement pattern of the light-receiving element. Therefore, there may be parts of the core arrangement pattern that do not correspond to the arrangement pattern of the light-emitting element or the arrangement pattern of the light-receiving element. Furthermore, at least a portion of the multiple cores and at least a portion of at least one of the multiple light-emitting elements and at least a portion of the multiple light-receiving elements may be optically coupled together. Therefore, some cores and light-emitting elements or light-receiving elements may be optically coupled individually rather than together.

[0057] Furthermore, the present invention is not limited by the embodiments described above. Configurations that appropriately combine the above-described components are also included in the present invention. Moreover, further effects and modifications can be easily derived by those skilled in the art. Therefore, broader aspects of the present invention are not limited to the embodiments described above, and various modifications are possible.

[0058] 100: Multicore fiber 101: Core 102: Cladding 200: Optical transceiver 210: Light source 211: Light-emitting element 220: Photodetector 221: Photodetector element 230: Optical coupling unit 240: Driver 250: Transimpedance amplifier (TIA) 260: Digital signal processor (DSP) 1000: Optical communication system S: Server

Claims

1. An optical communication system comprising: a multicore fiber made of plastic having a plurality of cores having a GI-type refractive index distribution arranged in a cross-section; a light source having a plurality of light-emitting elements arranged in an array; and a photodetector having a plurality of photodetectors arranged in an array, wherein the arrangement pattern of the plurality of cores in the multicore fiber corresponds at least partially to at least one of the arrangement pattern of the plurality of light-emitting elements in the light source and the arrangement pattern of the plurality of photodetectors in the photodetector, and at least a portion of the plurality of cores and at least a portion of at least one of the plurality of light-emitting elements and the plurality of photodetectors are optically coupled together as a whole.

2. The optical communication system according to claim 1, wherein the plurality of cores in the multicore fiber are arranged at a pitch of less than 250 μm.

3. The optical communication system according to claim 1, wherein the plurality of cores in the multicore fiber are arranged two-dimensionally.

4. The optical communication system according to claim 1, wherein the plurality of cores in the multicore fiber are arranged concentrically.

5. The number of cores per unit cross-sectional area in the multicore fiber is 16 / mm². ２ The optical communication system according to claim 1, wherein the above is true.

6. The optical communication system according to claim 1, wherein the light source includes a VCSEL array.

7. The optical communication system according to claim 1, wherein the light source includes a micro-LED array.

8. The optical communication system according to claim 1, wherein the product of the transmission rate and transmission distance in one of the cores of the multicore fiber is 450 Gbps·m or more.

9. The bandwidth density per unit cross-sectional area in the multicore fiber is 400 Gbit / s / mm². ２ The optical communication system according to claim 1, wherein the above is true.

10. The optical communication system according to claim 1, wherein the transmission rate in one of the cores of the multicore fiber is set such that the energy consumption per unit bit is 20 pJ / bit or less.

11. The optical communication system according to claim 1, wherein the variation in the received optical power required to achieve a predetermined bit error rate (BER) in the plurality of cores is 3 dB or less.

12. The optical communication system according to claim 1, wherein the degradation of the TDECQ (Transmitter and Dispersion Eye Closure Quaternary) in the multicore fiber is 3 dB or less.

13. The optical communication system according to claim 1, wherein the TDECQ (Transmitter and Dispersion Eye Closure Quaternary) is less than 4.4 dB.

14. The optical communication system according to claim 1, wherein the refractive index distribution coefficient g of the core is in the range of 1.50 to 3.

00.

15. The optical communication system according to claim 1, wherein the intercore crosstalk between adjacent cores in the multicore fiber is -30 dB or less.

Images