Optical communication system

Abstract

In a parallel optical communication system technology, there has been a problem that group delay times are generally different between wavelength channels and between spatial channels and that reception times of an optical clock signal and an optical main signal are misaligned.　An optical communication system 301 according to the present invention performs wavelength multiplexing and transmission of an optical main signal Lsig and an optical sub-signal (clock signal) Lclk to an optical transmission line 50. The optical communication system is characterized in that the optical main signal Lsig and the optical sub-signal Lclk are respectively assigned to a wavelength in a normal dispersion wavelength region and a wavelength in an abnormal dispersion wavelength region of the optical transmission line 50.

Description

Optical communication system

[0001] This disclosure relates to an optical communication system that transmits multiple optical signals in parallel.

[0002] With the development of artificial intelligence and machine learning technologies, the importance of image and video information acquired by cameras is increasing. Image recognition technology, which can accurately identify objects of interest from image and video data through image and video information processing, is attracting attention. This image recognition technology requires an image sensor 11 that receives light, an image signal processor 12 that generates an image, and an information processing base 13 based on the generated image (see Figure 1).

[0003] Image recognition technologies using artificial intelligence and machine learning require high-load signal processing and therefore consume a lot of power. For this reason, if an image signal processor or an information processing unit with a signal processing board is mounted on a camera, a robust power supply to the camera is necessary. However, power supply is a limiting factor in camera placement. Therefore, it is preferable to separate the image sensor and the information processing unit, allowing the sensor to be located at the shooting location and the information processing unit to be located in a remote location with abundant power. In the following explanation, "image signal processor" will be abbreviated as "image processor" or "processor."

[0004] For example, Non-Patent Document 1 discloses a camera that allows for the remote placement of an image sensor and an artificial intelligence-based signal processing board. Non-Patent Document 2 also discloses an interface that converts and transmits image sensor signals as Ethernet signals.

[0005] Nikon Product Introduction "Machine Vision Camera", https: / / digital-sol.nikon.com / products / cameras / (Accessed October 16, 2024) Thin Solutions Technology Overview V-by-one HS Technology, https: / / www.thinesollutions.com / v-by-one-hs-overview (Accessed September 26, 2024) "Demonstration of Timing Skew Compensation for Bit-Parallel WDM Data Transmission with PicoSecond Precision", S. Shen et al. , IEEE PHOTONICS TECHNOLOGY LETTERS, vol. 11, no. 5, pp. 566-568 (1999) “Comparing Inter-Core Skew Fluctuations in Multi-Core and Single-Core Fibers”, R. S. Luis et al. , CLEO SN2L. 5 (2015)

[0006] However, due to attenuation of electrical signal strength, the communication distance between the image sensor and the processor is limited to about 15 meters. Therefore, in order to expand the applicable range of camera installation locations, it is being considered to extend the communication distance by using low-loss optical communication between the image sensor and the processor.

[0007] Communication between the image sensor and the processor can use a format in which the clock signal and the main signal are transmitted in parallel. When the image sensor and the processor are connected by optical communication, the clock signal S ｃｌｋ and main signal S ｓｉｇ A method is envisioned in which the group delay time is assigned to the wavelength channel or spatial channel of the optical transmission path 50 and transmitted in parallel (see Figure 2). However, generally the group delay time differs between wavelength channels or spatial channels (see, for example, Non-Patent Documents 3 and 4). The difference in group delay time affects the optical clock signal L in the processor. ｃｌｋ and the main light signal L ｓｉｇThis causes signal skew, resulting in a delay in the reception time of the signals. The signal skew increases with increasing distance between the image sensor and the processor.

[0008] Due to this signal skew, extending the communication distance is difficult even when connecting the image sensor and processor with optical communication, which presents a challenge in expanding the applicable range of camera installation locations. Therefore, the present invention aims to provide an optical communication system that can improve signal skew in parallel transmission in order to solve the aforementioned problem.

[0009] To achieve the above objective, the optical communication system according to the present invention wavelength multiplexes optical signals to be transmitted in parallel, taking into account the wavelength characteristics of the group delay time of the optical transmission path.

[0010] Specifically, the optical communication system according to the present invention is an optical communication system that transmits an optical main signal and an optical sub-signal by wavelength multiplexing over an optical transmission path, characterized in that the optical main signal and the optical sub-signal are assigned to wavelengths in the normal dispersion wavelength range and wavelengths in the anomalous dispersion wavelength range of the optical transmission path, respectively.

[0011] Herein, the optical communication system according to the present invention is characterized in that the group delay times of the respective wavelengths assigned to the optical main signal and the optical sub-signal are equal. By selecting two wavelengths with equal group delay times from the normal dispersion wavelength range and the anomalous dispersion wavelength range of the optical fiber and assigning them as the transmission wavelengths for the optical main signal and the optical clock signal (optical sub-signal), the reception time difference between the optical clock signal and the optical main signal can be suppressed. Accordingly, the present invention can provide an optical communication system that can improve signal skew in parallel transmission.

[0012] Furthermore, the optical main signal and optical clock signal are not limited to one each. There can be multiple sets of optical main signals and optical clock signals, and for each set, two wavelengths with equal group delay times can be selected from the normal dispersion wavelength range and the anomalous dispersion wavelength range (resulting in two wavelengths with different group delay times for each set). If the optical transmission path has multiple uncoupled transmission channels, two wavelengths with the same group delay time can be assigned as the transmission wavelengths for the optical main signal and optical clock signal (optical sub-signal) for all sets.

[0013] Furthermore, the optical communication system according to the present invention may include a delay adjustment unit that adjusts the group delay times of the wavelengths assigned to the optical main signal and the optical sub-signal. For example, two wavelengths with similar group delay times are selected from the normal dispersion wavelength range and the anomalous dispersion wavelength range of the optical fiber and assigned as the transmission wavelengths for the optical main signal and the optical clock signal (optical sub-signal). The delay adjustment unit then adjusts the difference in group delay times between the optical main signal and the optical clock signal. This configuration makes it possible to suppress the difference in reception times between the optical clock signal and the optical main signal. Therefore, the present invention can provide an optical communication system that can improve signal skew in parallel transmission.

[0014] Note that the optical main signal and optical clock signal are not limited to one each. There may be multiple optical main signals for a single optical clock signal (each optical main signal may have a different wavelength). The delay adjustment unit adjusts the difference between the group delay time of the optical clock signal and the optical main signal for each optical main signal.

[0015] Specifically, another optical communication system according to the present invention is an optical communication system that transmits an optical main signal and an optical sub-signal by wavelength multiplexing in an optical transmission path, wherein the optical transmission path has a plurality of zero-dispersion wavelengths, and the optical main signal and the optical sub-signal are assigned to wavelengths with equal group delay times.

[0016] When using optical fibers with multiple zero-dispersion wavelengths as an optical transmission path, there are three or more wavelengths with equal group delay times. Therefore, by assigning one of these wavelengths to the optical clock signal and the others to the transmission wavelengths of multiple optical main signals, it is possible to suppress the reception time difference between the optical clock signal and the optical main signals. Accordingly, the present invention can provide an optical communication system that can improve signal skew in parallel transmission.

[0017] Furthermore, the above inventions can be combined as much as possible.

[0018] The present invention can provide an optical communication system that can improve signal skew in parallel transmission. In other words, the present invention can extend the communication distance of an optical communication system that transmits multiple optical signals in parallel, improve the flexibility of the connection between the image sensor and the image processor, and expand the range of applicable camera installation locations.

[0019] It is a diagram for explaining the configuration of an image recognition technology. It is a diagram for explaining the configuration of an image recognition technology using optical communication. It is a diagram for explaining an optical communication system according to the present invention. It is a diagram for explaining the wavelength dependence of the group delay time in an optical fiber. It is a diagram for explaining an optical communication system according to the present invention. It is a diagram for explaining the wavelength dependence of the group delay time in an optical fiber. It is a diagram for explaining an optical communication system according to the present invention. It is a diagram for explaining an optical communication system according to the present invention. It is a diagram for explaining the wavelength dependence of the group delay time in an optical fiber. It is a diagram for explaining an optical communication system according to the present invention. It is a diagram for explaining the wavelength dependence of the group delay time in an optical fiber. It is a diagram for explaining an optical communication system according to the present invention.

[0020] Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, components having the same reference numerals indicate the same components as each other.

[0021] (Embodiment 1) FIG. 3 is a diagram for explaining an optical communication system 301 of the present embodiment. The optical communication system 301 is an optical communication system that wavelength-division multiplexes and transmits an optical main signal L ｓｉｇ and an optical sub-signal (clock signal) L ｃｌｋ in an optical transmission line 50, and the optical main signal L ｓｉｇ and the optical sub-signal L ｃｌｋ are respectively assigned to wavelengths in the normal dispersion wavelength range and the anomalous dispersion wavelength range of the optical transmission line 50. In the present embodiment, the optical main signal L ｓｉｇ and the optical sub-signal L ｃｌｋ are each one, and a form in which the group delay times of the respective wavelengths assigned to the optical main signal L ｓｉｇ and the optical sub-signal L ｃｌｋ are equal will be described.

[0022] The optical communication system 301 includes an image sensor 11 in the camera unit 20, and an image processor 12 and a signal processing board 13 in the information processing unit 30. The camera unit 20 and the information processing unit 30 are arranged separately, and communication between them is performed via an optical transmission path 50. More specifically, optical transmitters 54a and 54b each receive a sub-signal (clock signal) S output from the image sensor 11. ｃｌｋ and main signal S ｓｉｇ The light main signal L ｓｉｇ and optical sub-signal (optical clock signal) L ｃｌｋ Convert to the optical main signal L. ｓｉｇ and optical sub-signal (clock signal) L ｃｌｋ The waves are combined by the multiplexer 51 and propagate through the optical transmission path 50 as wavelength-division multiplexed light. The wavelength-division multiplexed light is separated by the demultiplexer 52 and the optical main signal L ｓｉｇ The optical receiver 53b receives the optical sub-signal L ｃｌｋ The signal is received by the optical receiver 53a, converted into an electrical signal, and input to the image processor 12.

[0023] The optical transmission path 50 is a single-core optical fiber. While wavelength-division multiplexed light propagates through the optical transmission path 50, the optical main signal L ｓｉｇ The group delay time τ is due to its own wavelength. ｓｉｇ An optical sub-signal L occurs, ｃｌｋ The group delay time τ is due to its own wavelength. ｃｌｋ This occurs. Normally, τ ｓｉｇ ≠τ ｃｌｋ This is the cause of signal skew.

[0024] The wavelength dependence of the group delay time in optical fibers is determined by the structural dispersion and material dispersion of the core, and there exists a wavelength at which the group delay time is minimized. This is called the zero-dispersion wavelength, and there are regions of normal dispersion and anomalous dispersion with the zero-dispersion wavelength as the boundary.

[0025] Figure 4 shows the wavelength dependence of the group delay time in the most common single-mode optical fiber (core radius 4.2 μm, relative refractive index difference of core to cladding 0.35%). In this example, the zero-dispersion wavelength is λ ０ = 1.315 μm, λ ０ For this purpose, two wavelengths (for example, λ in the figure) have the same group delay time on the short wavelength side and the long wavelength side. ａｉ and λｎｉ (hereafter referred to as the "wavelength pair") can be selected. ｉ Achieving the wavelength pair λ ａｉ and λ ｎｉ Using these, the optical clock signals L ｃｌｋ and the main light signal L ｓｉｇ By transmitting this signal, the time difference in reception between the two signals can be suppressed.

[0026] In other words, the optical clock signal L can be seen from the graph in Figure 4. ｃｌｋ Wavelength and light principal signal L ｓｉｇ By appropriately selecting the wavelength of τ ｓｉｇ =τ ｃｌｋ This enables the reduction of signal skew.

[0027] Although this explanation uses a single-mode fiber as an example, similar wavelength selection can be performed in any wavelength band by optimally designing the zero-dispersion wavelength.

[0028] (Embodiment 2) In Embodiment 1, a configuration in which the image sensor 11 outputs one main signal was described, but in this embodiment, a configuration in which the image sensor 11 outputs multiple main signals is described. When the main signals are transmitted in parallel, pairs of optical clock signals and optical main signals are generated according to the number of lanes of the main signal. When the number of lanes is N (where N is an integer of 2 or more), each pair of optical clock signals and optical main signals has a different group delay time τ １ from τ Ｎ It is transmitted in wavelength pairs.

[0029] Figure 5 is a diagram illustrating the optical communication system 302 of this embodiment. The optical communication system 302 further includes a clock branching unit 14 and a transmission channel selection unit 15 compared to the optical communication system 301 of Embodiment 1. It also includes an optical transmitter (54a, 54b) and an optical receiver (53a, 53b) for each N main signal. The optical transmitters (54a, 54b) are located within the transmission channel selection unit 15.

[0030] Image sensor 11 receives clock signal S ｃｌｋ and N main signals (S ｓｉｇ１ ~S ｓｉｇＮ ) is output. Clock signal S ｃｌｋThe signal is branched into N parts at the clock branching section 14. The transmission channel selection section 15 selects N optical transmitters (54a １ ~54a Ｎ ) and N optical transmitters (54b １ ~54b Ｎ It has N wavelength pairs ([λ]) as shown in Figure 6. ａ１ , λ ｎ１ ] to [λ ａＮ , λ ｎＮ Find the following. In Embodiment 1, there is one wavelength pair, but in this embodiment, the number of wavelength pairs is N, which is the number of main signals.

[0031] Each optical transmitter (54a １ ~54a Ｎ ) is the wavelength (λ) of the optical clock signal in the wavelength pair. ａ１ ~λ ａＮ ) is set. Each optical transmitter (54a １ ~54a Ｎ ) is the input clock signal S ｃｌｋ Based on this, the set wavelength (λ ａ１ ~λ ａＮ ) optical clock signal (L ｃｌｋ１ ~L ｃｌｋＮ ) Output.

[0032] Each optical transmitter (54b １ ~54b Ｎ ) is the wavelength (λ) of the optical principal signal in the wavelength pair. ｎ１ ~λ ｎＮ ) is set. Each optical transmitter (54b １ ~54b Ｎ ) is the input main signal (S ｓｉｇ１ ~S ｓｉｇＮ Based on this, the set wavelength (λ ｎ１ ~λ ｎＮ ) Light main signal (L ｓｉｇ１ ~L ｓｉｇＮ ) Output.

[0033] These optical clock signals (L ｃｌｋ１ ~L ｃｌｋＮ ) and the main optical signal (L ｓｉｇ１ From L ｓｉｇＮ The waves are combined by the multiplexer 51 and propagate through the optical transmission path 50 as wavelength-division multiplexed light. The waves are then separated into individual wavelength channels by the demultiplexer 52 and transmitted to each receiver (53a１ to 53a Ｎ , 53b １ to 53b Ｎ are received by). The N clock signals (S ｃｌｋ１ to S ｃｌｋＮ ) and the N main signals (S ｓｉｇ１ to S ｓｉｇＮ ) are input to the image processor 12.

[0034] The image processor 12 can suppress the reception time deviation between the two signals by processing the paired clock signal and main signal. That is, by appropriately selecting the wavelengths of the optical clock signal and the optical main signal from the graph of FIG. 6, the difference in the group delay times of the two can be reduced, and the inter-signal skew can be reduced.

[0035] (Embodiment 3) In this embodiment, a form in which the main signals output by the image sensor 11 are plural and the optical transmission path 50 has two or more non-coupled transmission channels will be described. In this form, main signals of multiple lanes can be transmitted using the same wavelength pair. Non-coupled transmission channels can be realized by using two or more optical fibers, orthogonal polarization when a polarization-maintaining fiber is used as the optical transmission path, and cores and modes when a non-coupled space division multiplexed optical fiber is used as the optical transmission path. This embodiment is preferable because the number of transmission wavelengths can be reduced compared to Embodiment 2.

[0036] FIG. 7 is a diagram for explaining the optical communication system 303 of this embodiment. The optical communication system 303 includes an optical clock signal demultiplexing unit 24 as an alternative to the clock branching unit 14 with respect to the optical communication system 302 of Embodiment 2. Also, the transmission channel selection unit 15 has N optical transmitters 54b for the main signals, but only one optical transmitter 54a for the clock signal. In this embodiment, the number of main signals is N, but the number of wavelength pairs is only one of λ ａ and λ ｎ explained in FIG. 4.

[0037] From the image sensor 11, the clock signal S ｃｌｋ and N main signals (S ｓｉｇ１ to S ｓｉｇＮ ) are output. The optical transmitter 54a has the wavelength λ ａis set. The optical transmitter 54a outputs an optical clock signal L of a set wavelength λ based on the input clock signal S. ｃｌｋ The optical clock signal demultiplexing unit 24 demultiplexes the optical clock signal L into N branches. ａ The optical clock signal L ｃｌｋ is output. ｃｌｋ Each optical transmitter (54b

[0038] to 54b １ to 54b Ｎ ) has a set wavelength λ of the optical main signal of the wavelength pair. Each optical transmitter (54b ｎ to 54b １ to 54b Ｎ ) outputs an optical main signal (L ｓｉｇ１ to S ｓｉｇＮ ) of a set wavelength λ based on the input main signal (S ｎ to L ｓｉｇ１ to L ｓｉｇＮ ).

[0039] The multiplexer 51 multiplexes the optical main signal (L ｓｉｇ１ to L ｓｉｇＮ ) and N optical clock signals L ｃｌｋ and couples them to channels 1 to N of the optical transmission line 50. The demultiplexer 52 demultiplexes the optical main signal and the optical clock signal for each channel of the optical transmission line 50 and inputs them to the optical receivers ([53a １ , 53b １ to [53a Ｎ , 53b Ｎ ). The clock signal and the main signal output by each optical receiver are input to the image processor 12 for each channel ([S ｃｌｋ , S ｓｉｇ１ to [S ｃｌｋ , S ｓｉｇＮ ).

[0040] By the image processor 12 processing the paired clock signal and main signal, the reception time shift between the two signals can be suppressed. That is, by appropriately selecting the wavelength of the optical clock signal and the wavelength of the optical main signal from the graph of FIG. 4, the difference in the group delay time between the two can be reduced, and the inter-signal skew can be reduced.

[0041] (Embodiment 4) This embodiment describes a configuration in which the image sensor 11 outputs multiple main signals, and the optical transmission path 50 is an optical fiber having multiple zero-dispersion wavelengths. In this configuration, three or more wavelengths having the same group delay time can be selected. An optical fiber having multiple zero-dispersion wavelengths can be realized by applying a photonic crystal structure. This embodiment is also preferable because it can reduce the number of transmission wavelengths compared to Embodiment 2.

[0042] Figure 8 is a diagram illustrating the optical communication system 304 of this embodiment. The optical communication system 304 transmits multiple optical main signals (S) to the optical transmission path 50. ｓｉｇ１ ~S ｓｉｇＮ ) and optical sub-signal (clock signal) L ｃｌｋ An optical communication system that transmits signals by wavelength multiplexing, wherein the optical transmission path 50 has a plurality of zero-dispersion wavelengths, and the optical main signal and the optical sub-signal are assigned to wavelengths with equal group delay times.

[0043] The optical communication system 304 differs from the optical communication system 302 of Embodiment 2 in that it lacks a clock branching unit 14, and the transmission channel selection unit 15 has optical transmitters 54b for each main signal N, but only one optical transmitter 54a for the clock signal.

[0044] Image sensor 11 receives clock signal S ｃｌｋ and N main signals (S ｓｉｇ１ ~S ｓｉｇＮ The following is output: The optical transmitter 54a outputs the wavelength λ of the optical clock signal. ａ The setting is configured. The optical transmitter 54a receives the input clock signal S ｃｌｋ Based on this, the set wavelength λ ａ Optical clock signal L ｃｌｋ Outputs.

[0045] Each optical transmitter (54b １ ~54b Ｎ ) is the wavelength λ of the light principal signal. ｎ This is configured. Each optical transmitter (54b １ ~54b Ｎ ) is the input main signal (S ｓｉｇ１ ~S ｓｉｇＮ Based on this, the set wavelength λ ｎLight main signal (L ｓｉｇ１ ~L ｓｉｇＮ ) Output.

[0046] Figure 9 illustrates the wavelength characteristics of the group delay time in a photonic crystal optical fiber. In this figure, the zero-dispersion wavelength number is 3. In the case of such wavelength characteristics, the group delay time is τ ｉ The number of wavelengths is 5 (the number of wavelengths varies depending on the group delay time). For example, when an optical fiber with N-1 zero-dispersion wavelengths is used as the optical transmission path 50, N wavelengths with the same group delay time can be selected. In the optical communication system 302 of Embodiment 2, 2N wavelengths are required, including the clock signal, to transmit the main signal in N lanes. On the other hand, the optical communication system 304 of this embodiment can transmit the main signal in N lanes with N+1 wavelengths. That is, optical transmitter 54a and optical transmitter (54b １ ~54b Ｎ The wavelengths set in ) are the respective wavelengths of the optical fiber that have the same group delay time.

[0047] Optical clock signal L from transmission channel selection unit 15 ｃｌｋ and light main signal (L ｓｉｇ１ ~L ｓｉｇＮ The waves are combined by the multiplexer 51 and propagate through the optical transmission path 50 as wavelength-division multiplexed light. The waves are then separated into individual wavelength channels by the demultiplexer 52 and transmitted to the optical receiver 53a and the optical receiver (53b １ ~53b Ｎ The light is received by ). Each receiver outputs one clock signal (S ｃｌｋ１ ~S ｃｌｋＮ ) and N main signals (S ｓｉｇ１ ~S ｓｉｇＮ ) is input to the image processor 12.

[0048] The image processor 12 processes this clock signal and the main signal, thereby suppressing the reception time difference between the two signals. In other words, by appropriately selecting the wavelength of the optical clock signal and the wavelength of the optical main signal as shown in the graph of Figure 9, the difference in group delay time between the two can be reduced, thereby reducing signal skew.

[0049] Furthermore, by using a distributed flat optical fiber as the optical transmission path 50, the number of lanes for transmitting the main signal can be further increased.

[0050] (Embodiment 5) Even with an optical transmission path having a single zero-dispersion wavelength (Figure 4), such as a general-purpose single-mode optical fiber, by providing a delay control unit for each channel, it is possible to transmit optical main signals from multiple lanes with a single optical clock signal.

[0051] Figure 10 is a diagram illustrating the optical communication system 305 of this embodiment. Compared to the optical communication system 302 of Embodiment 2, the optical communication system 305 lacks the clock branching unit 14 and includes a delay adjustment unit 27 that adjusts the group delay time of the wavelengths assigned to the optical main signal and the optical sub-signal. Furthermore, the transmission channel selection unit 15 has as many optical transmitters 54b as there are main signals (N), but only one optical transmitter 54a for the clock signal.

[0052] Image sensor 11 receives clock signal S ｃｌｋ and N main signals (S ｓｉｇ１ ~S ｓｉｇＮ The following is output: The optical transmitter 54a outputs the wavelength λ of the optical clock signal. ａ The setting is configured. The optical transmitter 54a receives the input clock signal S ｃｌｋ Based on this, the set wavelength λ ａ Optical clock signal L ｃｌｋ Outputs.

[0053] Each optical transmitter (54b １ ~54b Ｎ ) is the wavelength (λn) of the main optical signal. １ ~λn Ｎ ) is set. Each optical transmitter (54b １ ~54b Ｎ ) is the input main signal (S ｓｉｇ１ ~S ｓｉｇＮ Based on this, the set wavelength λ ｎ Light main signal (L ｓｉｇ１ ~L ｓｉｇＮ ) Output.

[0054] Figure 11 illustrates the wavelength characteristics of the group delay time of the optical transmission line 50. Optical transmitter 54a and optical transmitter (54b１ ~54b Ｎ The wavelengths set in the region are as follows: As shown in Figure 11, the wavelength λa of the optical clock signal is set to the anomalous dispersion region, and the wavelength (λn) of the optical main signal is set to the region. １ ~λn Ｎ The wavelength λa of the optical clock signal is selected from the normal dispersion region, and the wavelength (λn) of the optical main signal is selected from the normal dispersion region. １ ~λn Ｎ ) may be selected from the above distributed domains.

[0055] Optical clock signal L from transmission channel selection unit 15 ｃｌｋ and light main signal (L ｓｉｇ１ ~L ｓｉｇＮ The waves are combined by the multiplexer 51 and propagate through the optical transmission path 50 as wavelength-division multiplexed light. The waves are then separated into individual wavelength channels by the demultiplexer 52 and transmitted to the optical receiver 53a and the optical receiver (53b １ ~53b Ｎ It is received by ).

[0056] The delay adjustment unit 27 adjusts the received signal (clock signal S) output by each optical receiver. ｃｌｋ and main signal (S ｓｉｇ１ ~S ｓｉｇＮ The time difference (difference in group delay time) is adjusted. At this time, the amount of adjustment for the time difference can be determined by pre-measuring the wavelength dispersion of the optical transmission line 50.

[0057] Figure 10 shows an example configuration in which the electrical signal received by the optical receiver is delayed. As another example, an optical delay adjustment unit with optical delay lines may be placed between the optical transmitter 54 and the multiplexer 51, between the demultiplexer 52 and the optical receiver 53, or both, to adjust the time difference optically.

[0058] A single clock signal with delay adjustment (S ｃｌｋ１ ~S ｃｌｋＮ ) and N main signals (S ｓｉｇ１ ~S ｓｉｇＮ The signal is input to the image processor 12. The image processor 12 processes this clock signal and the main signal to suppress the reception time difference between the two signals. In other words, the delay adjustment unit 27 reduces the difference in group delay time and reduces signal skew.

[0059] (Embodiment 6) Based on the configurations of Embodiments 1 to 5 described above, it is possible to connect multiple image sensors and multiple image processors in a mesh configuration. Figure 12 illustrates an optical communication system 306 that connects two image sensors (11-1, 11-2) and three image processors (12-1 to 12-3) as an example. The number of image sensors, the number of image processors, and the symmetry or asymmetry of their connections are not limited.

[0060] The signals (clock signal and main signal) from the image sensors (11-1, 11-2) are transmitted to the optical transmitter group (54-1, 54-2) as described in Embodiments 1 to 5, and consist of an optical clock signal and an optical main signal (wavelength λ). １１ ~λ １ｋ , λ ２１ ~λ ２ｋ The output is an optical signal. The optical transmitter group (54-1, 54-2) is the optical transmitter (54a, 54a) described in Embodiments 1 to 5. １ ~54a Ｎ , 54b, 54b １ ~54b Ｎ This is a combined representation of the above. The optical signal is combined by the multiplexer 51 and input to the optical transmission line as wavelength-division multiplexed light. After the wavelength-division multiplexed light propagates through the transmission line 50, it is separated into individual wavelengths by the demultiplexer 52.

[0061] The path control unit 29 controls each of the separated wavelengths (λ １１ ~λ １ｋ , λ ２１ ~λ ２ｋ The optical signal of the optical receiver (53-1 to 53-3) is routed to distribute to an arbitrary image processor. The route control unit 29 is, for example, a wavelength-selective switch. The optical receiver group (53-1 to 53-3) generates received signals (clock signals, main signals) from the signal light as described in Embodiments 1 to 5. The optical receiver group (53-1 to 53-3) is a group of optical receivers (53a, 53a) as described in Embodiments 1 to 5. １ ~53a Ｎ , 53b, 53b １ ~53b Ｎ This is a collective representation of ).

[0062] The optical communication system 306 can transmit signals from any image sensor to image processors with different performance characteristics. Therefore, it is preferable that multiple image sensors can share various image processors, thereby economically enabling the enhancement of the camera system's functionality.

[0063] [Note] This invention relates to a parallel optical communication system technology that handles a clock signal and a main signal in parallel and transmits them via an optical transmission path that involves E / O conversion and O / E conversion in the intermediate transmission section. Parallel optical communication system technology generally has the problem that the group delay time differs between wavelength channels and spatial channels, causing a delay in the reception times of the optical clock signal and the optical main signal. This invention solves this problem with the following configuration.

[0064] [Configuration 1] An optical communication system characterized by communicating using two or more wavelength channels, wherein one or more wavelength channels are arranged on the short-wavelength side and the long-wavelength side of the zero-dispersion wavelength of the optical transmission path, with at least one of the wavelength channels used as a clock signal and the other wavelength channels used as the main transmission signal.

[0065] [Configuration 2] (Clock branching, multiplexing on uncoupled channels other than wavelength) The optical communication system according to Configuration 1, characterized in that it has an optical clock signal branching unit for branching a clock signal and means for multiplexing a plurality of main transmission signals on the same wavelength.

[0066] [Configuration 3] (Delay Adjustment Unit) The optical communication system according to Configurations 1 and 2, further comprising means for canceling out the delay time between the clock signal and the main transmission signal based on the communication delay wavelength dependence of the optical transmission path.

[0067] [Configuration 4] (Camera IF) An image acquisition system characterized in that communication between an image sensor and an image signal processor is performed by the optical communication system described in Configurations 1 to 3.

[0068] 11, 11-1, 11-2: Image sensor 12, 12-1, 12-2, 12-3: Image processor 13: Signal processing board 14: Clock branching unit 15: Transmission channel selection unit 20: Camera 24: Optical clock signal demultiplexer 27: Delay adjustment unit 29: Path control unit 30: Information processing unit 50: Optical transmission line 51: Multiplexer 52: Demultiplexer 53a, 53a １ ~53a Ｎ Optical receivers for clock signals 53-1, 53-2, 53-3; Optical receiver group 54a, 54a １ ~54a Ｎ : Optical transmitters for clock signals 54-1, 54-2: Group of optical transmitters

Claims

1. An optical communication system that transmits a primary optical signal and a secondary optical signal by wavelength multiplexing over an optical transmission path, characterized in that the primary optical signal and the secondary optical signal are assigned to wavelengths in the normal dispersion wavelength range and wavelengths in the anomalous dispersion wavelength range of the optical transmission path, respectively.

2. The optical communication system according to claim 1, characterized in that the group delay times of the respective wavelengths assigned to the optical main signal and the optical sub-signal are equal.

3. The optical communication system according to claim 1, further comprising a delay adjustment unit that adjusts the group delay time of the respective wavelengths assigned to the optical main signal and the optical sub-signal.

4. An optical communication system that transmits a primary optical signal and a secondary optical signal by wavelength multiplexing over an optical transmission path, wherein the optical transmission path has a plurality of zero-dispersion wavelengths, and the primary optical signal and the secondary optical signal are assigned to wavelengths with equal group delay times.

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