JP2013037016A - Mode multiplexer/demultiplexer, optical transmitting and receiving device, and optical communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve precision of mode multiplexing, and reduce transmission loss when multiplexing.SOLUTION: A mode multiplexer 3 for generating an optical signal x having a plurality of modes, includes: input parts 31-1, 31-2, 31-3,..., 31-N for inputting optical signals x, x, x,..., xhaving each of the modes; an output part 32 for outputting the optical signal x having the plurality of modes; and a multiplexing unit that reflects the optical signals x, x, x,..., xhaving each of the modes from an incident direction from the input parts 31-1, 31-2, 31-3,..., 31-N to an emission direction to the output part 32, by utilizing FBGs 34-1, 34-2, 34-3,..., 34-N which reflect the optical signals x, x, x,..., xhaving each of the modes, to generate the optical signal x having the plurality of modes.

Description

  The present invention relates to a technique for generating or demultiplexing an optical signal having a plurality of modes in an optical communication system using a multimode optical fiber.

  Currently, traffic in optical fiber networks is increasing, and transmission capacity has been expanded using various methods such as transmission speed increase, multi-level modulation technology, and wavelength division multiplexing (WDM). However, expansion of the transmission capacity using existing transmission lines and conventional transmission methods is expected to become difficult in the future, so expansion of the wavelength region and new transmission methods are being studied.

  As a method for expanding the wavelength region, studies have been made to increase the transmission capacity by realizing WDM in a wide wavelength region using a wavelength band that is not currently used. However, since the transmission loss varies depending on the wavelength band, the usable wavelength band is considered to be limited. Furthermore, since it is difficult to realize an optical amplifier that can amplify over a wide wavelength range, there are many problems in realizing WDM in a wide wavelength range. Therefore, in addition to WDM, a mode multiplexing method using a plurality of modes by using a multimode optical fiber as a transmission path has been proposed (for example, Patent Document 1, Non-Patent Document 1, and Non-Patent Document 2). reference).

JP-A-8-288911

C. P. Tsekrekos and A.M. M.M. J. et al. Koonen, “Mode-selective spatial filtering for increased robustness in a mode group diversity multiplexing link,” Opt. Lett. 32, 1041-1043 (2007). S. Savin, M .; J. et al. F. Digonnet, G.M. S. Kino and H. J. et al. Shaw, “Tunable mechanically induced long-period fiber gratings,” Opt. Lett. 25, 710-712 (2000).

  However, Patent Document 1 and Non-Patent Document 2 do not propose a method for exciting a desired higher-order mode. Also in Non-Patent Document 1, mode coupling is performed by varying the excitation position in the optical fiber for each mode, and mode separation is performed by varying the reception position in the optical fiber for each mode. In other words, no precise mode multiplexing / demultiplexing method and multiple mode multiplexing / demultiplexing methods have been proposed, and loss and crosstalk between multiplexed signals exist, making it difficult to realize long-distance and large-capacity transmission. There is a problem.

  Therefore, in order to solve the above-described problems, an object of the present invention is to improve the accuracy of mode multiplexing and demultiplexing, and to reduce loss at the time of multiplexing and crosstalk at the time of demultiplexing.

  In order to achieve the above object, at the time of mode combination, a fiber Bragg grating that reflects an optical signal having each mode is used, and the output unit common to each mode is determined from the incident direction from the input unit for each mode. The optical signal having each mode is reflected in the emission direction. And at the time of mode demultiplexing, using a fiber Bragg grating that reflects an optical signal having each mode, from the incident direction from the input unit common to each mode, to the output direction to the output unit for each mode, The optical signal having each mode is reflected.

  Specifically, the present invention is a mode multiplexer that generates an optical signal having a plurality of modes, and that inputs an optical signal having each mode and outputs the optical signal having the plurality of modes. And an output unit that uses the fiber Bragg grating that reflects the optical signal having each mode, and reflects the optical signal having each mode from the incident direction from the input unit to the output direction to the output unit, And a multiplexing unit that generates an optical signal having the plurality of modes.

  The present invention is also a mode multiplexer for generating an optical signal having a plurality of modes, an input unit for inputting the optical signal having each mode, and an output unit for outputting the optical signal having the plurality of modes. And using each of the plurality of modes other than the single mode by using a fiber Bragg grating that reflects an optical signal having each of the modes other than the single mode. An optical signal is reflected from an incident direction from the input unit to an output direction to the output unit, and an optical signal having the single mode among the plurality of modes is reflected by the fiber Bragg grating. And a multiplexing unit that generates an optical signal having the plurality of modes by being guided from the input unit to the output unit. It is a mode multiplexer.

  According to this configuration, it is possible to provide a mode multiplexer that improves the accuracy of mode multiplexing, reduces loss during multiplexing, and extends the transmission distance.

  The present invention is also a mode demultiplexer for demultiplexing an optical signal having a plurality of modes, an input unit for inputting the optical signal having the plurality of modes, and an output for outputting the optical signal having each mode. And a fiber Bragg grating that reflects the optical signal having each mode, and reflects the optical signal having each mode from the incident direction from the input unit to the output direction to the output unit. And a demultiplexing unit for demultiplexing an optical signal having the following modes.

  The present invention is also a mode demultiplexer for demultiplexing an optical signal having a plurality of modes, an input unit for inputting the optical signal having the plurality of modes, and an output for outputting the optical signal having each mode. And a fiber Bragg grating that reflects an optical signal having each mode other than a single mode among the plurality of modes, and each mode other than the single mode among the plurality of modes. Reflecting the optical signal having the single mode out of the plurality of modes by the fiber Bragg grating, and reflecting the optical signal having an incident direction from the input unit to the output direction to the output unit. And a demultiplexing unit that demultiplexes the optical signal having the plurality of modes by being guided from the input unit to the output unit. It is a mode demultiplexer.

  According to this configuration, it is possible to provide a mode demultiplexer that improves the accuracy of mode demultiplexing, reduces crosstalk during demultiplexing, and extends the transmission distance.

  In addition, the present invention provides a generation unit that generates each of optical signals having different modes, a mode multiplexer that generates the optical signals having the plurality of modes, and an optical signal having the plurality of modes combined. An optical transmission device comprising: a transmission unit that transmits

  According to this configuration, it is possible to provide an optical transmission apparatus that improves the accuracy of mode multiplexing, reduces loss during multiplexing, and extends the transmission distance.

  Further, the present invention provides a receiving unit that receives an optical signal having a plurality of combined modes, a mode demultiplexer that demultiplexes the optical signal having a plurality of modes, and an optical signal having a different mode. And a processing unit for processing the optical receiver.

  According to this configuration, it is possible to provide an optical receiver that improves the accuracy of mode demultiplexing, reduces crosstalk during demultiplexing, and extends the transmission distance.

  The present invention also provides an optical transmitter, an optical receiver, a multimode optical fiber that connects the optical transmitter and the optical receiver, and transmits an optical signal having a plurality of combined modes. An optical communication system is provided.

  According to this configuration, it is possible to provide an optical communication system that improves the accuracy of mode multiplexing and demultiplexing, reduces loss at the time of multiplexing and crosstalk at the time of demultiplexing, and extends the transmission distance.

  The present invention improves the accuracy of mode multiplexing and demultiplexing, and can reduce loss during multiplexing and crosstalk during demultiplexing.

It is a figure which shows the structure of an optical communication system. It is a figure which shows the 1st structure of a mode multiplexer. It is a figure which shows the 2nd structure of a mode multiplexer. It is a figure which shows the 3rd structure of a mode multiplexer. It is a figure which shows the 4th structure of a mode multiplexer. It is a figure which shows the 1st structure of a mode splitter. It is a figure which shows the 2nd structure of a mode splitter. It is a figure which shows the 3rd structure of a mode splitter. It is a figure which shows the 4th structure of a mode splitter. It is a figure which shows the relationship between the use wavelength and effective refractive index in each mode. It is a figure which shows the relationship between the FBG period and use wavelength in each mode.

  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, the same reference numerals denote the same components.

(Configuration of optical communication system)
The configuration of the optical communication system is shown in FIG. In the optical communication system, a mode multiplexing method is applied using N (N is a natural number of 2 or more) modes, and transmitters 1-1, 1-2, ..., 1-N, mode converter 2- 1, 2-2, ..., 2-N, mode multiplexer 3, multimode optical fiber 4, mode duplexer 5 and receivers 6-1, 6-2, ..., 6-N Composed.

The transmitters 1-1, 1-2, ..., 1-N, the mode converters 2-1, 2-2, ..., 2-N, and the mode multiplexer 3 constitute an optical transmission device. ing. The transmitters 1-1, 1-2, ..., 1-N and the mode converters 2-1, 2-2, ..., 2-N correspond to the generation unit and have different modes. Each of the optical signals x ₁ , x ₂ ,..., X _N is generated. The mode multiplexer 3 generates an optical signal x having a plurality of modes.

The mode demultiplexer 5 and the receivers 6-1, 6-2,..., 6-N constitute an optical receiver. The mode demultiplexer 5 demultiplexes the optical signal y having a plurality of modes. Receiver 6-1 and 6-2, ..., 6-N corresponds to the processing section, each _{y 1,} y 2 of optical signals having different modes, ..., to process _{y N} .

  The multimode optical fiber 4 connects the transmission side and the reception side, and transmits an optical signal x or y having a plurality of combined modes. The transmitters 1-1, 1-2,..., 1-N generate optical signals having the same wavelength and fundamental mode. The mode converters 2-1, 2-2,..., 2 -N convert the optical signal having the basic mode into an optical signal having a different mode.

ここで、ｎ_０は、使用波長λにおける基本モードの実効屈折率を示しており、ｎ_１ ^ｍは、使用波長λにおけるｍ番目の高次モードの実効屈折率を示している。 The mode converters 2-1, 2-2,..., 2-N can be realized by using a long period fiber Bragg grating (FBG). As shown in Non-Patent Document 2, in order to convert the fundamental mode to a higher-order mode at the used wavelength λ, the interval Λ of the periodic refractive index change of the FBG is set as in Equation 1.

Here, n ₀ represents the effective refractive index of the fundamental mode at the used wavelength λ, and n ₁ ^m represents the effective refractive index of the mth higher-order mode at the used wavelength λ.

The interval Λ of periodic refractive index change of the FBG is determined by the structural parameter of the optical fiber to be used, the wavelength λ to be used, and the mode order m to be converted. After determining the wavelength λ to be used, numerical analysis is performed from the structural parameters of the optical fiber to calculate the effective refractive index n ₀ of the fundamental mode and the effective refractive index n ₁ ^m of the desired higher-order mode, and n obtained by calculation Substituting ₀ and n ₁ ^m into Equation 1 to determine the interval Λ of the required refractive index change of the FBG. In order to convert the fundamental mode to the first higher-order mode at a wavelength of 1.550 μm, which will be described later, the interval Λ of the periodic refractive index change of the FBG is set to Λ = 711.1 μm.

(Configuration of mode multiplexer)
A first configuration of the mode multiplexer is shown in FIG. The first mode multiplexer 3 is applied as the mode multiplexer 3 of FIG. 1, and includes input units 31-1, 31-2, 31-3, ..., 31-N, an output unit 32, and an optical circulator. 33-1, 33-2, 33-3,..., 33-N, and FBGs 34-1, 34-2, 34-3,.

Input unit 31-1, 31-2, 31-3, · · ·, 31-N, respectively, the optical signals _x 1 with each _mode, x _2, x 3, · · ·, and inputs the _{x N.} The output unit 32 outputs an optical signal x having a plurality of modes. FBG34-1,34-2,34-3, ···, 34-N, respectively, the optical signals _x 1 with each _mode, x _2, x 3, · · ·, a _{x N,} the input unit 31-1 , 31-2, 31-3,..., 31-N are reflected from the incident direction to the output unit 32. Optical circulator 33-1,33-2,33-3, ···, 33-N optical signals _x 1 with each respective _mode, x _2, x 3, · · ·, a _{x N,} in FBG34 Before reflection, the light is guided from the input units 31-1, 31-2, 31-3,..., 31-N to the FBGs 34-1, 34-2, 34-3,. After the reflection, the light is guided from the FBGs 34-1, 34-2, 34-3,..., 34-N to the output unit 32.

  A second configuration of the mode multiplexer is shown in FIG. The second mode multiplexer 3 is applied as the mode multiplexer 3 of FIG. 1, and includes input units 31-1, 31-2, 31-3, ..., 31-N, an output unit 32, and an optical coupler. , 35-N, and FBGs 34-1, 34-2, 34-3,..., 34-N. That is, instead of the optical circulators 33-1, 33-2, 33-3, ..., 33-N, optical couplers 35-1, 35-2, 35-3, ..., 35-N are arranged. You can also

  FIG. 4 shows a third configuration of the mode multiplexer. The 3rd mode multiplexer 3 is applied as the mode multiplexer 3 of FIG. 1, and the input parts 31-1, 31-2, 31-3, ..., 31-N, 31- (N + 1), The output unit 32, the optical circulators 33-1, 33-2, 33-3,..., 33-N, and the FBGs 34-1, 34-2, 34-3,. .

The input units 31-1, 31-2, 31-3,..., 31-N, 31- (N + 1) are optical signals x ₁ , x ₂ , x ₃ ,. _N and xN _{+ 1} are input. The output unit 32 outputs an optical signal x having a plurality of modes. Each of the FBGs 34-1, 34-2, 34-3,..., 34-N has optical signals x ₁ , x ₂ , x ₃ ,. - the _{x N,} the input unit 31-1, ..., to reflect the incident direction from 31-N to the exit direction to the output unit 32. The optical signal xN _{+ 1} having a single mode among the plurality of modes is not reflected by the FBGs 34-1, 34-2, 34-3,..., 34-N, and is input to the input unit 31- (N + 1). To the output unit 32. The optical circulators 33-1, 33-2, 33-3,..., 33-N are optical signals x ₁ , x ₂ , x ₃ , each having a mode other than a single mode among a plurality of modes. ..., and _{x N,} before reflection at the FBG34 input section 31-1,31-2,31-3, ···, FBG34-1,34-2,34-3 from 31-N, ·· .., 34 -N, and after being reflected by the FBG 34, are guided from the FBGs 34-1, 34-2, 34-3,..., 34 -N to the output unit 32.

  A fourth configuration of the mode multiplexer is shown in FIG. The 4th mode multiplexer 3 is applied as the mode multiplexer 3 of FIG. 1, and the input parts 31-1, 31-2, 31-3, ..., 31-N, 31- (N + 1), , 35-N, and FBGs 34-1, 34-2, 34-3,..., 34-N. . That is, instead of the optical circulators 33-1, 33-2, 33-3, ..., 33-N, optical couplers 35-1, 35-2, 35-3, ..., 35-N are arranged. You can also

  Thus, in the present invention, unlike Non-Patent Document 1, mode coupling is not performed by changing the excitation position in the optical fiber for each mode, and FBG 34 and (optical circulator 33 or optical coupler 35) are used. Mode multiplex. Therefore, it is possible to provide a mode multiplexer that improves the accuracy of mode multiplexing, reduces loss during multiplexing, and extends the transmission distance.

(Configuration of mode duplexer)
A first configuration of the mode duplexer is shown in FIG. The first mode demultiplexer 5 is applied as the mode demultiplexer 5 of FIG. 1, and includes an input unit 51, output units 52-1, 52-2, 52-3,..., 52-N, an optical circulator. 53-, 53-2, 53-3,..., 53-N, and FBGs 54-1, 54-2, 54-3,.

The input unit 51 inputs an optical signal y having a plurality of modes. Output unit 52-1,52-2,52-3, ···, 52-N, respectively, the optical signals _y 1 with each _mode, y _2, y 3, · · ·, and outputs a _{y N.} FBG54-1,54-2,54-3, ···, 54-N, respectively, the optical signals _y 1 with each _mode, y _2, y 3, · · ·, a _{y N,} from the input unit 51 Reflected in the emission direction from the incident direction to the output units 52-1, 52-2, 52-3, ..., 52-N. Optical circulator 53-1,53-2,53-3, ···, 53-N optical signals _y 1 with each respective _mode, y _2, y 3, · · ·, a _{y N,} in FBG54 Before reflection, the light is guided from the input unit 51 to the FBGs 54-1, 54-2, 54-3,..., 54-N, and after being reflected by the FBG 54, the FBGs 54-1, 54-2, 54-3,. .., 54-N is guided to output units 52-1, 52-2, 52-3,.

  A second configuration of the mode duplexer is shown in FIG. The second mode demultiplexer 5 is applied as the mode demultiplexer 5 of FIG. 1, and includes an input unit 51, output units 52-1, 52-2, 52-3,..., 52-N, and an optical coupler. , 55-N, and FBGs 54-1, 54-2, 54-3,..., 54-N. That is, instead of the optical circulators 53-1, 53-2, 53-3,..., 53-N, optical couplers 55-1, 55-2, 55-3,. You can also

  FIG. 8 shows a third configuration of the mode duplexer. The third mode demultiplexer 5 is applied as the mode demultiplexer 5 of FIG. 1 and includes an input unit 51, output units 52-1, 52-2, 52-3, ..., 52-N, 52-. (N + 1), optical circulators 53-1, 53-2, 53-3,..., 53-N, and FBGs 54-1, 54-2, 54-3,. .

The input unit 51 inputs an optical signal y having a plurality of modes. The output units 52-1, 52-2, 52-3,..., 52-N, 52- (N + 1) are optical signals y ₁ , y ₂ , y ₃ ,. _N and yN _{+ 1} are output. Each of the FBGs 54-1, 54-2, 54-3,..., 54-N has optical signals y ₁ , y ₂ , y ₃ ,. · the _{y N,} the output unit 52-1,52-2,52-3 the incident direction from the input unit 51, ..., to reflect the emission direction of the 52-N. The optical signal y _{N + 1} having a single mode among the plurality of modes is not reflected by the FBGs 54-1, 54-2, 54-3,. -(N + 1) is guided. Each of the optical circulators 53-1, 53-2, 53-3,..., 53-N has optical signals y ₁ , y ₂ , y ₃ having a mode other than a single mode among the plurality of modes. .., Y _N is guided from the input unit 51 to the FBGs 54-1, 54-2, 54-3,..., 54-N before being reflected by the FBG 54, and after being reflected by the FBG 54, the FBG 54- 1, 54-2, 54-3,..., 54-N are guided to output units 52-1, 52-2, 52-3,.

  A fourth configuration of the mode duplexer is shown in FIG. The fourth mode demultiplexer 5 is applied as the mode demultiplexer 5 of FIG. 1, and includes an input unit 51, output units 52-1, 52-2, 52-3, ..., 52-N, 52-. (N + 1), optical couplers 55-1, 55-2, 55-3,..., 55-N, and FBGs 54-1, 54-2, 54-3,. . That is, instead of the optical circulators 53-1, 53-2, 53-3,..., 53-N, optical couplers 55-1, 55-2, 55-3,. You can also

  Thus, in the present invention, unlike the non-patent document 1, the reception position on the optical fiber is not changed for each mode, and mode separation is not performed, and the FBG 54 and (the optical circulator 53 or the optical coupler 55) are used. Mode demultiplexing. Therefore, it is possible to provide a mode demultiplexer that improves the accuracy of mode demultiplexing, reduces loss during demultiplexing, reduces crosstalk, and extends the transmission distance.

(FBG parameters)
The parameters of the FBG 34 or 54 are set so that the mode multiplexer 3 or the mode duplexer 5 is realized. In the following description, the setting of the parameters of the FBG 34 or 54 will be described by taking as an example a case where two modes, that is, the basic mode and the first higher-order mode exist.

ここで、λ_ｐは、使用波長を示しており、ｎ_ｅｆｆは、実効屈折率を示しており、Λは、ＦＢＧ３４又は５４の周期的な屈折率変化の間隔を示している。 The relationship between the wavelength used and the effective refractive index in each mode is shown in FIG. The core radius a = 7 μm, the relative refractive index difference Δ = 0.4% with respect to the cladding of the core, and there are two modes of LP01 mode and LP11 mode at wavelengths of 1.53 to 1.56 μm. The reflection condition at the FBG 34 or 54 is expressed as Equation 2.

Here, λ _p indicates the wavelength used, n _eff indicates the effective refractive index, and Λ indicates the periodic refractive index change interval of the FBG 34 or 54.

Please refer to FIG. 10 and Equation 2 together. When Λ is 0.5353 μm, the reflection wavelength of the LP01 mode is 1.550 μm, and the reflection wavelength of the LP11 mode is 1.548 μm. When Λ is 0.536 μm, the reflection wavelength of the LP01 mode is 1.552 μm, and the reflection wavelength of the LP11 mode is 1.550 μm. Therefore, the wavelength used is λ _p = 1.550 μm, and the interval between periodic refractive index changes of the FBG 34 or 54 is Λ = 0.536 μm and 0.5353 μm. Then, in the FBG 34 or 54 in which Λ = 0.536 μm, the optical signal having the LP11 mode is reflected, but the optical signal having the LP01 mode is not reflected. In the FBG 34 or 54 in which Λ = 0.5353 μm, the optical signal having the LP01 mode is reflected, but the optical signal having the LP11 mode is not reflected.

FIG. 11 shows the relationship between the FBG period and the used wavelength in each mode. The upper part of FIG. 11 is data relating to the wavelength region near from the above-described λ _p = 1.550 μm, and the lower part of FIG. 11 is data relating to the wavelength region far from the above-described λ _p = 1.550 μm. The Λ corresponding to the LP01 mode and the LP11 mode is different not only at the use wavelength of λ _p = 1.550 μm but also at the use wavelength far from λ _p = 1.550 μm.

つまり、図１０に挙げた例において、各ＦＢＧ３４又は５４において各モードを反射させるときには、Δλが２ｎｍ以下となるようにΔｎ及びｌを適切に設定する。一般には、ＦＢＧ３４又は５４の反射帯域を数ｎｍの帯域とすることができるため、各モードを個別に反射する各ＦＢＧ３４又は５４は、現状の技術で実現可能であることが分かる。 The reflection band Δλ of the FBG 34 or 54 is expressed as Equation 3 by the amplitude Δn and the region 1 with respect to the change in the refractive index grating of the FBG 34 or 54.

That is, in the example shown in FIG. 10, when each mode is reflected by each FBG 34 or 54, Δn and l are appropriately set so that Δλ is 2 nm or less. Generally, since the reflection band of the FBG 34 or 54 can be set to a band of several nanometers, it can be seen that each FBG 34 or 54 that individually reflects each mode can be realized by the current technology.

(Combination of mode multiplexing method and WDM)
In the above embodiment, the mode multiplexing method is applied using a single wavelength. However, as a modification example below, the mode multiplexing method and WDM may be used in combination with a plurality of wavelengths. . At this time, each FBG 34 or 54 that individually reflects an optical signal having each wavelength and each mode may be applied to the mode multiplexer 3 or the mode demultiplexer 5.

  The mode multiplexer / demultiplexer, optical transmission / reception apparatus, and optical communication system according to the present invention can be applied not only to the mode multiplexing method but also to the mode multiplexing method and other multiplexing methods (such as WDM and polarization multiplexing). It can be applied to the method.

1: transmitter 2: mode converter 3: mode multiplexer 4: multimode optical fiber 5: mode demultiplexer 6: receiver 31: input unit 32: output unit 33: optical circulator 34: FBG
35: Optical coupler 51: Input unit 52: Output unit 53: Optical circulator 54: FBG
55: Optical coupler

Claims (7)

A mode multiplexer for generating an optical signal having a plurality of modes,
An input unit for inputting an optical signal having each mode;
An output unit for outputting an optical signal having the plurality of modes;
Using a fiber Bragg grating that reflects the optical signal having each mode, the optical signal having each mode is reflected from the incident direction from the input unit to the output direction to the output unit, and the plurality of modes are A multiplexing unit for generating an optical signal having,
A mode multiplexer comprising: A mode multiplexer for generating an optical signal having a plurality of modes,
An input unit for inputting an optical signal having each mode;
An output unit for outputting an optical signal having the plurality of modes;
An optical signal having each of the plurality of modes other than the single mode using a fiber Bragg grating that reflects an optical signal having each of the modes other than the single mode. Without reflecting the optical signal having the single mode out of the plurality of modes by the fiber Bragg grating, while reflecting from the incident direction from the input unit to the output direction to the output unit. A multiplexing unit that generates an optical signal having the plurality of modes by being guided from the input unit to the output unit;
A mode multiplexer comprising: A mode duplexer for demultiplexing an optical signal having a plurality of modes,
An input unit for inputting an optical signal having the plurality of modes;
An output unit for outputting an optical signal having each mode;
Using a fiber Bragg grating that reflects the optical signal having each mode, the optical signal having each mode is reflected from the incident direction from the input unit to the output direction to the output unit, and the plurality of modes are A demultiplexing unit for demultiplexing an optical signal having;
A mode duplexer comprising: A mode duplexer for demultiplexing an optical signal having a plurality of modes,
An input unit for inputting an optical signal having the plurality of modes;
An output unit for outputting an optical signal having each mode;
An optical signal having each of the plurality of modes other than the single mode using a fiber Bragg grating that reflects an optical signal having each of the modes other than the single mode. Without reflecting the optical signal having the single mode out of the plurality of modes by the fiber Bragg grating, while reflecting from the incident direction from the input unit to the output direction to the output unit. A demultiplexing unit for demultiplexing the optical signal having the plurality of modes by guiding from the input unit to the output unit;
A mode duplexer comprising: A generator for generating each of the optical signals having different modes;
The mode multiplexer according to claim 1 or 2, which generates an optical signal having the plurality of modes.
A transmitter that transmits the optical signal having the plurality of modes combined;
An optical transmission device comprising: A receiver for receiving an optical signal having a plurality of combined modes;
The mode demultiplexer according to claim 3 or 4, which demultiplexes the optical signal having the plurality of modes.
A processing unit for processing each of the optical signals having different modes;
An optical receiving device comprising: An optical transmitter according to claim 5;
An optical receiver according to claim 6;
A multimode optical fiber that connects the optical transmitter and the optical receiver and transmits an optical signal having a plurality of combined modes;
An optical communication system comprising:

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