JP2009268029A - Light transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light transmission system in which connection between optical fibers and connection between an optical fiber and apparatus are easily carried out, and for which an expensive component is unnecessary. <P>SOLUTION: A transmission device 2 has photo-signal output portions 16-1 to 16-N where a plurality of wavelengths are arranged in order, and a receiving device 6 has a plurality of light receiving elements 34-1 to 34-N. A plurality of the photo-signal output portions 16-1 to 16-N outputs a signal of a predetermined pattern in training. A weight calculation portion 28 calculates the weight to obtain a signal transmitted by the transmission device 2 from a signal received after ending the training based on the signal received in a plurality of the light receiving elements 34-1 to 34-N in training. An information signal presumption portion 24 presumes a signal transmitted by the transmission device 2 from the signal received in a plurality of the light receiving elements 34-1 to 34-N correspondingly to the calculated weight after ending the training. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical transmission system, and more particularly to an optical transmission system using a multimode optical fiber.

  In recent years, in the field of wireless communication, on the transmission side, transmission data is distributed and transmitted to a plurality of antennas, and a radio signal that has arrived via a propagation path is received on the reception side using a plurality of antennas. A communication method (MIMO: Multiple Input Multiple Output) for restoring the original information signal from the received signal is used (see, for example, Patent Document 1).

On the other hand, in optical transmission using an optical fiber, a single mode optical fiber cable with a single light path (mode) through which light propagates and a multimode with multiple light paths (modes) through which light propagates are used. Some use optical fiber cables. The multimode optical fiber cable has a problem that a penalty due to mode dispersion is large because there are a plurality of modes. In contrast, single-mode optical fibers do not incur penalties due to mode dispersion, and have the advantage of enabling high-quality and stable communication. Optical transmission is widely used.
JP 2003-198442 A

  However, optical communication using a single mode optical fiber has the following problems.

  First, since the single mode optical fiber has a small core system, there is a problem that it is not easy to connect the optical fibers and connect the optical fiber and the device.

  In addition, since serial transmission using a single mode optical fiber requires high-speed communication, it is necessary to provide expensive components.

  In addition, wavelength-division-multiplexed parallel transmission using a single-mode optical fiber, wavelength-controlled light sources (and sometimes temperature control required) and filters, and expensive components such as light-receiving elements that can receive only specific wavelength signals is required.

  Therefore, an object of the present invention is to provide an optical transmission system in which connection between optical fibers and connection between an optical fiber and a device are easy and an expensive component is not required.

  In order to solve the above-described problems, the present invention provides an optical transmission system in which a transmission device and a reception device are connected by a multimode optical fiber, and the transmission device emits light having a plurality of wavelengths. A plurality of lights are modulated by a predetermined pattern during training, and the receiving device receives a plurality of lights transmitted through the multimode optical fiber, and during training, Based on the signal received by the light receiving unit, the weight calculating unit for calculating the weight for obtaining the signal transmitted by the transmitting device from the signal received after the training is completed, and the light receiving unit received by the light receiving unit according to the calculated weight after the training is completed An estimation unit that estimates a signal transmitted from the signal by the transmission device.

  Preferably, the light emitting unit includes a plurality of light sources, each light source outputs one of a plurality of light having a uniform wavelength, the plurality of light sources are two-dimensionally arranged, and are multimode. It is optically coupled to the optical fiber at once.

  Preferably, the light receiving unit includes a plurality of light receiving elements, each of the light receiving elements receives one of a plurality of light having a uniform wavelength, and the plurality of light receiving elements are two-dimensionally arranged. And it is optically coupled to the multimode optical fiber at once.

  Preferably, the light emitting unit includes a first planar lightwave circuit, and the first planar lightwave circuit outputs a plurality of light having the same wavelength, and the first planar lightwave circuit and the multimode optical fiber are provided. Optically coupled.

  Preferably, the light receiving unit includes a second planar lightwave circuit, and the second planar lightwave circuit includes a plurality of light receiving elements that each receive one of a plurality of light having a uniform wavelength. The light receiving elements are optically coupled to the multimode optical fiber at once.

  According to the optical transmission system of the present invention, the connection between the optical fibers and the connection between the optical fiber and the device are easy, and expensive components are not required.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings.
(Constitution)
FIG. 1 is a configuration diagram of an optical transmission system according to an embodiment of the present invention.

  With reference to FIG. 1, in this optical transmission system, a transmission device 2 and a reception device 6 are connected by a multimode optical fiber 4.

  The transmission device 2 includes an information signal output unit 8, a training signal output unit 10, an FFT unit 12, a light emitting unit 14, and a lens 18.

For example, the training signal output unit 10 outputs a serial training signal having a value of “0” or “1” during training. Training signal is located N set (N is a natural number of 2 or more), one set is made from the N signal, training signal s ₁ of the j-th _{set, s 2, ..., s j} , ..., s N is A signal is selected such that a signal sf _j = 1 and sf _k = 0 (k = 1 to N, k ≠ j) after Fourier transform described later.

  The information signal output unit 8 outputs a serial information signal having a value of “0” or “1” other than during training. Here, the information signal means a signal other than the training signal and including information to be transmitted from the transmission side to the reception side.

The FFT unit 12 receives the serial information signal or the training signal, performs time-space conversion (Fourier transform) every N (s ₁ , s ₂ , s ₃ ,..., S _N ), and outputs the parallel signal [sf ₁ , sf ₂ , sf ₃ ,..., Sf _N ] are output.

The light emitting unit 14 outputs N pieces of light having the same wavelength.
FIG. 2 is a diagram illustrating an overview of the light emitting unit 14 and the lens 18 and the multimode optical fiber 4 in the transmission device 2.

Referring to FIG. 2, the light emitting unit 14 includes a semiconductor laser 150, a branching device 151 that distributes light emitted from the semiconductor laser 150 into N pieces, and signals sf ₁ , sf ₂ , sf ₃ ,..., sf _{N and N} modulators 152-1 to 152-N, and N optical signal output units (light sources) 16- arranged two-dimensionally on a silicon plate (chip) 153 1-16-N. Further, the light emitting unit 14 guides the light emitted from the semiconductor laser 150 to the branching device 151 and guides the light distributed by the branching device 151 to the N modulators 152-1 to 152-N. Waveguides 154-1 to 154-N and waveguides 155-1 to 155-N for guiding the light modulated by the modulators 152-1 to 152-N to the optical signal output units 16-1 to 16-N. .

  The N optical signal output units 16-1 to 16-N are two-dimensionally arranged so that the propagation mode of the fiber can be used and a more independent propagation path can be used. Each of the optical signal output units 16-1 to 16-N includes, for example, a mirror.

  Each of the optical signal output units 16-1 to 16-N outputs one of N lights having the same wavelength. That is, each of the optical signal output units 16-1 to 16-N outputs laser light modulated according to one corresponding signal among N parallel signals. For example, each of the optical signal output units 16-1 to 16-N increases the emission intensity when the corresponding signal is “0”, and decreases the emission intensity when the corresponding signal is “1”. The N optical signal output units 16-1 to 16-N output laser beams (signals) in synchronization.

  The lens 18 guides the laser beams output from the N optical signal output units 16-1 to 16 -N to the core of the multimode optical fiber 4. That is, the N optical signal output units 16-1 to 16 -N are optically coupled to the multimode optical fiber 4 at once.

  The multimode optical fiber 4 transmits the light output from the transmission device 2 to the reception device 6. Specifically, the multimode optical fiber 4 is a step index multimode optical fiber in which the refractive index changes discontinuously only at the interface between the core and the grad, or the refractive index of the core is a quadratic function with respect to the radial direction. Graded index multimode optical fiber can be used. The material of the multimode optical fiber 4 is, for example, quartz glass, plastic, or resin. The multimode optical fiber 4 may be twisted or bent so that a larger number of modes are generated.

  Referring again to FIG. 1, receiving device 6 includes lens 20, light receiving unit 30, A / D conversion unit 32, weight calculation unit 28, information signal estimation unit 24, and IFFT unit 26. .

  The light receiving unit 30 receives N pieces of light having the same wavelength transmitted through the multimode optical fiber 4.

  FIG. 3 is a diagram illustrating an overview of the multimode optical fiber 4 and the lens 20 and the light receiving unit 30 in the receiving device 6.

  Referring to FIG. 3, light receiving unit 30 includes N photodiodes (light receiving elements) 34-1 to 34-N arranged two-dimensionally on silicon chip 157.

  The lens 20 guides the light emitted from the core 46 of the multimode optical fiber 4 to the photodiodes 34-1 to 34-N of the light receiving unit 30. That is, the N photodiodes (light receiving elements) 34-1 to 34-N are optically coupled to the multimode optical fiber 4 at once.

  By arranging the photodiodes (light receiving elements) 34-1 to 34-N in a two-dimensional manner, it becomes possible to utilize the propagation mode of the fiber, and to use a more independent propagation path. Further, the optical signal output unit 16 The maximum independence of the propagation path can be obtained by making the arrangement of −1 to 16-N also two-dimensional.

  Each of the photodiodes 34-1 to 34-N receives one of N lights having the same wavelength, converts the received optical signal into an analog electric signal, and outputs an electric signal line 159-1 to 159-1. The data is output to the A / D converter 32 via 159N. N photodiodes 34-1 to 34-N perform signal conversion in synchronization.

  The A / D converter 32 includes N A / D converters 36-1 to 36 -N. Each A / D converter 36-1 to 36-N converts an analog signal from the connected photodiode 34-1 to 34-N into a digital signal.

  At the time of training, the weight calculation unit 28 calculates a weight for obtaining the information signal transmitted by the transmission device 2 from the signal received after the training based on the signal from the A / D conversion unit 32.

By the way, a plurality of signals sf ₁ , sf ₂ ,... Sf _N input to the light emitting unit 14 of the transmission device 2 and a plurality of signals r ₁ , r ₂ output from the A / D conversion unit 32 of the reception device 6. ,..., R _N , the following equation holds.

R = H × Sf (1)
Here, Sf = (sf ₁ , sf ₂ ,..., Sf _N ) ^T and R = (r ₁ , r ₂ ,..., R _N ) ^T. H is called a propagation path matrix. Where x ^T represents the transpose of the vector x. Each element of Sf is obtained by transforming the transmission signal S into the frequency domain (Fourier transform), and includes a delay time (phase delay) by expressing the propagation path matrix in the multimode optical fiber as a complex number. It is possible to express the propagation path characteristics.

Time-space conversion is performed by applying a weight matrix W to the received signals [r ₁ , r ₂ ,..., R _N ] of the information signal output from the A / D converter 32 of the receiving device 6 as shown in the following equation. Sf ′ ₁ , sf ′ ₂ ,..., Sf ′ _N after (Fourier transform) are obtained, and further, the IFFT unit 26 performs space-time transform (inverse Fourier transform) to obtain the serial signal. By outputting, the estimated values s ′ ₁ , s ′ ₂ ,..., S ′ _N of the information signal can be obtained.

Sf ′ = W × R (2)
Where R = (r ₁ , r ₂ ,..., R _N ) ^T ,
Sf ′ = (sf ′ ₁ , sf ′ ₂ ,..., Sf ′ _N ) ^T ,
If a weight matrix W such that W × H is E (unit matrix) is obtained from the equations (1) and (2), Sf ′ coincides with Sf.

Each element h _ij of the propagation path matrix H is obtained by training. For example, it can be obtained as follows. Here, a case where N = 3 will be described as an example.

When the information signal is sf ₁ = 1 and sf ₂ = sf ₃ = 0, Sf = (1, 0, 0) ^T , and R at this time is (h ₁₁ , h ₂₁ , h ₃₁ ) ^T. .

When the information signal is sf ₂ = 1 and sf ₁ = sf ₃ = 0, Sf = (0, 1, 0) ^T , and R at this time is (h ₁₂ , h ₂₂ , h ₃₂ ) ^T .

When the information signal is sf ₃ = 1 and sf ₂ = sf ₃ = 0, Sf = (0,0,1) ^T , and R at this time becomes (h ₁₃ , h ₂₃ , h ₃₃ ) ^T. .

According to the training as described above, the value of the received signal can be used as the value of each element h _ij of the propagation path matrix H as it is.

Next, a specific configuration of the weight calculation unit 28 will be described.
The weight calculation unit 28 includes a propagation path matrix specifying unit 40, a propagation path matrix storage unit 42, and a weight matrix calculation unit 44.

The propagation path matrix specifying unit 40 propagates r _i in the signals r ₁ , r ₂ ,..., R _N for the j-th set of training signals as elements h _ij (i = 1 to N) of the propagation path matrix H. Store in the route matrix storage unit 42.

The propagation path matrix storage unit 42 stores values of elements h _ij (i = 1 to N, j = 1 to N) of the propagation path matrix H of N rows and N columns.

The weight matrix calculation unit 44 calculates a weight matrix W of N rows and N columns by calculating an inverse matrix of the propagation path matrix H stored in the propagation path matrix storage unit 42, and each element w of the weight matrix W the value of _ij, supplied as one input of a corresponding multiplier MU _ij information signal estimation unit 24.

After the training, the information signal estimation unit 24 uses the weight matrix W and the received signals r ₁ , r ₂ ,..., R _N according to the above equation (2) to estimate information signals sf ′ ₁ , sf ′. ₂ ,..., Sf ′ _N is calculated.

FIG. 4 is a diagram illustrating a specific configuration example of the information signal estimation unit 24.
Referring to FIG. 4, the information signal estimation unit 24 includes N × N multipliers MU _ij (i = 1 to N, j = 1 to N) and N adders AD _i (i = 1 to N). N).

Multiplier MU _ij calculates the product of weight w _ij and received signal r _j and outputs product w _ij × r _j to adder AD _i .

The adder AD _i calculates w _i1 × r ₁ + w _i2 × r ₂ +... + W _iN × r _N and outputs the calculation result as an estimated value s ′ _i of the information signal.

(Sending training procedure)
FIG. 5 is a flowchart showing the operation procedure of the training process of the transmission apparatus 2.

  Referring to FIG. 5, first, training signal output unit 10 sets control variable j = 1 (step S101).

Next, the training signal output unit 10, a training signal of the serial _{s 1, s 2, ...,} s j, ..., and outputs the s _N. However, s ₁ , s ₂ ,..., S _j ,..., S _N are selected so that, for example, sf _j = 1 and sf _k = 0 (k = 1 to N, k ≠ j) after Fourier transform ( Step S102).

Then, FFT unit 12 receives the serial training signal every N _{(s 1, s 2, ...} , s j, ..., s N) in time - performs spatial transformation (Fourier transform), parallel signal [Sf ₁ , sf ₂ ,..., Sf _j ,..., Sf _N ] are output (step S103).

Then, the optical signal output section 16-1 to 16-N of the i-th (1 ≦ i ≦ N) outputs a laser beam corresponding to the value of the signal sf _i (step S104).

  Next, the training signal output unit 10 increments the control variable j (step S105), and ends when the control variable j exceeds N (YES in step S106), and ends when the control variable j is N or less (step S106). NO), the process returns to step S102.

(Receiving side training process)
FIG. 6 is a flowchart showing the operation procedure of the training process of the receiving device 6.

  Referring to FIG. 6, propagation path matrix specifying unit 40 sets control variable j = 1 (step S202).

Next, each of the photodiodes 34-1 to 34-N converts the received light into an analog electrical signal, and the A / D converters 36-1 to 36-1 connected to the photodiodes 34-1 to 34-N. 36-N converts parallel electric signals [r ₁ , r ₂ ,..., R _N ] of the parallel number N in the entire light receiving unit 30 and the A / D conversion unit 32 by converting analog electric signals into digital signals. Output (step S203).

The propagation path matrix specifying unit 40 stores r _i in r ₁ , r ₂ ,..., R _N as elements h _ij (i = 1 to N) of the propagation path matrix H in the propagation path matrix storage unit 42 (steps). S204).

  Next, the propagation path matrix specifying unit 40 increments the control variable j (step S206). When the control variable j exceeds N (YES in step S206), the process proceeds to step S207. When the control variable j is N or less, (NO in step S206), the process returns to step S203.

Next, the weight matrix calculation unit 44 uses h _ij (i = 1 to N, j = 1 to N) stored in the propagation channel matrix storage unit 42 as each element of the propagation channel matrix H, and propagates the propagation channel. A weight matrix W that is an inverse matrix of the matrix H is calculated (step S207).

Next, the weight matrix calculation unit 44 supplies each element w _ij of the weight matrix W as a calculation result to the corresponding multiplier of the information signal estimation unit 24 (step S208).

(Transmission side information signal transmission processing procedure)
FIG. 7 is a flowchart showing an operation procedure of information signal transmission processing of the transmission apparatus 2.

Referring to FIG. 7, first, information signal output unit 8 outputs serial information signal sequences s ₁ , s ₂ ,..., S _N (step S301).

Next, the FFT unit 12 receives a serial information signal sequence (s ₁ , s ₂ ,..., S _N ), performs time-space conversion (Fourier transform), and performs parallel signals [sf ₁ , sf ₂ ,. , sf _N ] is output (step S302).

Then, the optical signal output section 16-1 to 16-N of the i-th (1 ≦ i ≦ N) outputs a laser beam corresponding to the value of the signal sf _i (step S303).

(Reception side information signal estimation processing procedure)
FIG. 8 is a flowchart showing the operation procedure of the information signal estimation process of receiving apparatus 6.

Referring to FIG. 8, each of the photodiodes 34-1 to 34-N converts the received light into an analog electrical signal, and an A / D converter connected to the photodiodes 34-1 to 34-N. 36-1 to 36 -N convert analog electric signals into digital signals, so that the entire number of parallel signals [r ₁ , r ₂ ,. r _N ] is output (step S401).

Next, the information signal estimation unit 24 outputs the parallel signals [r ₁ , r ₂ ,..., R _N ] output from the A / D conversion unit 32 and the weights w ₁₁ and w output from the weight matrix calculation unit 44. ₁₂ ,..., W _NN are used to calculate estimated values [sf ′ ₁ , sf ′ ₂ ,..., Sf ′ _N ] of parallel information signals according to the equation (2) (step S 402).

Next, the IFFT unit 26 receives the parallel signals [sf ′ ₁ , sf ′ ₂ ,..., Sf ′ _N ] from the information signal estimation unit 24 and performs space-time conversion (inverse Fourier transform) to obtain a serial sequence. s ′ ₁ , s ′ ₂ ,..., s ′ _N are output (step S403).

  As described above, according to the optical transmission system of the embodiment of the present invention, by using a plurality of optical signal output units (light sources), a plurality of photodiodes, and a multimode optical fiber having a large diameter, wireless communication is possible. The used MIMO scheme can also be applied to optical communication. Since multimode optical fiber is used, the connection between optical fibers and the connection between optical fiber and equipment can be facilitated, and even if some propagation modes are interrupted due to incomplete connection, transmission is completely completed. You can avoid being blocked. In addition, since a plurality of signals are transmitted in parallel, high-speed optical transmission can be realized without requiring expensive parts.

  Furthermore, since a plurality of optical signal output units and photodiodes are two-dimensionally arranged on one chip, a plurality of optical signal output units and photodiodes having the same characteristics can be easily manufactured.

(Modification)
The present invention is not limited to the above-described embodiment, and includes, for example, the following modifications.

(1) Light Source In the embodiment of the present invention, the light emitting unit is configured to include one semiconductor laser and N optical signal output units (light sources), but the present invention is not limited to this. The light emitting unit may be configured such that N semiconductor lasers (light sources) that output light of the same wavelength are two-dimensionally arranged on a semiconductor chip.

(2) Silicon plate (chip) for light emitting part
In the embodiment of the present invention, the N optical signal output units are two-dimensionally arranged on the silicon plate (chip), but the present invention is not limited to this. For example, the optical signal output unit may be two-dimensionally arranged on a glass plate or a polymer plate.

(3) Branching In the embodiment of the present invention, the optical signal output unit (light source) and the photodiode are two-dimensionally arranged on one chip. However, the present invention is not limited to this. For example, a multi-mode optical fiber may be branched at a certain location, and one or a plurality of light sources (semiconductor laser or optical signal output unit) or photodiodes may be arranged at each branched end.

FIG. 9 is a diagram illustrating a modification of the optical transmission system.
Referring to FIG. 9, in this optical transmission system, a multimode optical fiber is branched and coupled by optical splitter / couplers 64 and 66. Transmitters 68, 70, and 72 are connected to the ends of the multimode optical fibers 52, 54, and 56 branched by the optical splitter / coupler 64, respectively. Receiving devices 74, 76, and 78 are connected to the ends of the multimode optical fibers 58, 60, and 62 branched by the optical splitter / coupler 66, respectively.

  Each of the transmitting devices 68, 70, 72 includes one light source 80, 82, 84, and each of the receiving devices 74, 76, 78 includes one photodiode 86, 88, 90, respectively.

The transmission devices 68, 70, 72 are connected to each other by a wireless or wired electric line, and transmit signals in cooperation. The transmitter 68 outputs laser light corresponding to the signal s ₁ to the multimode optical fiber 52. Similarly, the transmitter 70 outputs laser light corresponding to the signal s ₂ to the multimode optical fiber 54. Similarly, the transmitter 72 outputs a laser beam corresponding to the signal s ₃ to the multimode optical fiber 56.

The receiving device 74 generates a received signal r ₁ based on the laser light from the multimode optical fiber 58. The receiving device 76 generates a reception signal r ₂ based on the laser light from the multimode optical fiber 60. The reception device 78 generates a reception signal r ₃ based on the laser light from the multimode optical fiber 62.

The receiving devices 74, 76, and 78 are connected to each other by a wireless or wired electric line, and cooperate to calculate the weight and estimate the information signal by using the received signals r ₁ , r ₂ , and r _3. Do.

(4) Number of optical signal output units, number of photodiodes, calculation of weight, estimation of information signal In the embodiment of the present invention, the number of optical signal output units and the number of photodiodes are the same, but this is not limitative. It may be different, not. Further, the weight calculation and information signal estimation described in the embodiment of the present invention are merely examples, and the present invention is not limited to this, and other methods may be used.

(5) PLC (Planar Lightwave Circuit)
Further, the connection method between the multimode optical fiber, the light emitting unit, and the light receiving unit is not limited to the coupling by the space as described in the embodiment.

  FIG. 10 is a diagram illustrating an overview of the light emitting unit 194 and the lens 18 and the multimode optical fiber 4 according to a modification of the transmission device.

  Referring to FIG. 10, light emitting unit 194 includes a planar lightwave circuit 192 that outputs N pieces of light having the same wavelength.

The planar optical circuit 192 includes a semiconductor laser 250, a branching device 258 that distributes the light emitted from the semiconductor laser 250 into N pieces, and the distributed light as signals sf ₁ , sf ₂ , sf ₃ ,. _N modulators 252-1 to 252-N that modulate according to sf _N and a combiner 257 that combines the N modulated lights.

  Further, the planar lightwave circuit 192 guides the light emitted from the semiconductor laser 250 to the branching device 258 and the light distributed by the branching device 258 to the N modulators 252-1 to 252-N. Waves 251-1 to 251-N, waveguides 253-1 to 253-N that guide light modulated by the modulators 252-1 to 252-N to the coupler 257, and light coupled by the coupler 257 And a waveguide 254 for transmitting.

  The lens 18 guides the laser light output from the end of the waveguide 254 of the planar lightwave circuit 192 to the core of the multimode optical fiber 4. That is, the planar lightwave circuit 192 is optically coupled to the multimode optical fiber 4.

  FIG. 11 is a diagram illustrating an overview of the multimode optical fiber 4, the lens 20 in the receiving apparatus, and the light receiving unit 230 of the modification.

Referring to FIG. 11, light receiving unit 230 includes a planar lightwave circuit 232.
The planar lightwave circuit 232 includes N photodiodes (light receiving elements) 234-1 to 234-N.

  The planar lightwave circuit 232 further includes a waveguide 235 that guides N light having a uniform wavelength emitted from the lens 20, a branching device 237 that distributes the light transmitted through the waveguide 235 into N, and a branching device. And waveguides 239-1 to 239 -N that guide the N lights distributed by 237 to photodiodes (light receiving elements) 234-1 to 234 -N.

  The lens 20 transmits light emitted from the core 46 of the multimode optical fiber 4 to the photodiodes 234-1 to 234-N via the waveguide 235, the branching device 237, and the waveguides 239-1 to 239-N. Lead. That is, N photodiodes (light receiving elements) 234-1 to 234-N are optically coupled to the multimode optical fiber 4 at once.

  Each of the photodiodes 234-1 to 234 -N receives one of the N lights having the same wavelength, converts the received light signal into an analog electric signal, and outputs an electric signal line 159-1. The data is output to the A / D converter 32 via 159N. N photodiodes 234-1 to 234-N perform signal conversion in synchronization.

  By performing joint distribution on the PLC as described above, difficulty in spatial coupling can be alleviated, and cost reduction and yield improvement can be expected.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a block diagram of the optical transmission system of embodiment of this invention. It is a figure showing the general view of the light emission part and lens in a transmitter, and a multimode optical fiber. It is a figure showing the general appearance of the lens in a multimode optical fiber, a receiver, and a light-receiving part. It is a figure showing the specific structural example of an information signal estimation part. It is a flowchart showing the operation | movement procedure of the training process of a transmitter. It is a flowchart showing the operation | movement procedure of the training process of a receiver. It is a flowchart showing the operation | movement procedure of the transmission process of the information signal of a transmitter. It is a flowchart showing the operation | movement procedure of the estimation process of the information signal of a receiver. It is a figure showing the modification of an optical transmission system. It is a figure showing the general view of the light emission part and lens of a modification in a transmitter, and a multimode optical fiber. It is a figure showing the general view of the multimode optical fiber, the lens in a receiver, and the light-receiving part of a modification.

Explanation of symbols

2, 68, 70, 72 Transmitter, 4, 50, 52, 54, 56, 58, 60, 62 Multimode optical fiber, 6, 74, 76, 78 Receiver, 8 Information signal output unit, 10 Training signal output Unit, 12 FFT unit, 14,194 light emitting unit, 16-1 to 16-N optical signal output unit (light source), 80, 82, 84 light source, 18, 20 lens, 24 information signal estimation unit, 38 IFFT unit, 28 Weight calculation unit, 30, 230 light receiving unit, 32 A / D conversion unit, 34-1 to 34-N, 86, 88, 90, 234-1 to 234-N photodiode, 36-1 to 36-NA / D converter, 40 propagation path matrix specifying section, 42 propagation path matrix storage section, 44 weight matrix calculation section, 46 core, MU _{11 to} MU _NN multiplier, AD _{11 to} AD _NN adder 64, 66 optical branching / combining unit 150, 25 0 semiconductor laser, 151, 237, 258 branching device, 152-1 to 151-N, 252-1 to 252-N modulator, 153 silicon plate (chip), 157 silicon chip, 154-1 to 154-N, 155 -1 to 155-N, 181, 182, 251-1 to 251-N, 235, 239-1 to 239-N, 253-1 to 253-N, 254 waveguide, 159-1 to 159-N electrical signal Line, 192, 232 Planar lightwave circuit, 257 coupler.

Claims (5)

An optical transmission system in which a transmission device and a reception device are connected by a multimode optical fiber,
The transmitter is
Equipped with a light emitting unit that outputs a plurality of light with a uniform wavelength,
The plurality of lights are modulated by a predetermined pattern during training,
The receiving device is:
A light receiving unit for receiving the plurality of lights transmitted through the multimode optical fiber;
Based on the signal received by the light receiving unit during training, a weight calculating unit that calculates a weight for obtaining a signal transmitted by the transmitting device from a signal received after the end of training,
An optical transmission system comprising: an estimation unit that estimates a signal transmitted by the transmission device from a signal received by the light receiving unit according to the calculated weight after the end of training. The light emitting unit includes a plurality of light sources,
Each light source outputs one of a plurality of lights having the same wavelength,
The optical transmission system according to claim 1, wherein the plurality of light sources are two-dimensionally arranged and optically coupled to the multimode optical fiber at once. The light receiving unit includes a plurality of light receiving elements,
Each light receiving element receives one of a plurality of lights having the same wavelength,
The optical transmission system according to claim 1, wherein the plurality of light receiving elements are two-dimensionally arranged and optically coupled to the multimode optical fiber at a time. The light emitting unit includes a first planar lightwave circuit,
The first planar lightwave circuit outputs a plurality of lights having the same wavelength,
The optical transmission system according to claim 1 or 3, wherein the first planar lightwave circuit and the multimode optical fiber are optically coupled. The light receiving unit includes a second planar lightwave circuit,
The second planar lightwave circuit includes a plurality of light receiving elements that each receive one of the plurality of lights having the same wavelength,
5. The optical transmission system according to claim 1, wherein the plurality of light receiving elements are optically coupled to the multimode optical fiber at a time.

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