JP2010141680A - Optical multiplexing apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical multiplexing apparatus for reducing, as far as possible, bands unavailable for communication inside communication bands. <P>SOLUTION: The optical multiplexing apparatus includes first to Nth optical interleavers (N is an integer of ≥2) and a photo coupler for multiplexing output signals of the first to Nth optical interleavers. When K is an integer from 1 to N, inside a band to be used for communication, an optical interleaver that uses the block band of a Kth optical interleaver as a transmission band is present among the first to Nth optical interleavers. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technique for multiplexing optical signals having different wavelengths.

  In order to multiplex optical signals of different wavelengths, an arrayed waveguide grating (AWG) is mainly used, but a configuration in which AWG and an optical interleaver are combined to further increase the number of multiplexing. Has been proposed (see Non-Patent Document 1, for example).

[Online], [Search on November 26, 2008], Internet <URL: http: // www. optoplex. com / Optical_Interleaver. htm>

FIG. 4 is a block diagram of a multiplexing apparatus combining an AWG and an optical interleaver. In FIG. 4, the AWG 21 multiplexes the optical signals of the three wavelengths λ ₁ , λ ₅ and λ ₉ and outputs a signal having the optical spectrum of FIG. 5A, and the AWG 22 has the wavelengths λ ₃ , λ ₇ and λ ₁₁ are multiplexed to output a signal having the optical spectrum shown in FIG. 5B, and the interleaver 1 interleaves the signals shown in FIGS. 5A and 5B. A signal having an optical spectrum shown in FIG. 5C is output.

  The interleaver 1 includes two input terminals and one output terminal, and is configured such that the transmission band characteristics viewed from each input terminal are the characteristics shown in FIG. In FIG. 6, the characteristic indicated by the solid line is the transmission band characteristic viewed from the input terminal to which the AWG 21 is connected, and the characteristic indicated by the dotted line is the transmission band characteristic viewed from the input terminal to which the AWG 22 is connected. . As shown in FIG. 6, the transmission band characteristics are comb-shaped, that is, the transmission band and the stop band are configured to appear alternately and periodically in a band used for wavelength multiplexing communication. The interval between the center frequency of each and the center frequency of the adjacent transmission band is called the channel optical frequency interval.

As shown in FIG. 6, the transmission band characteristic viewed from one input terminal of the interleaver 1 is shifted by half the channel optical frequency interval from the transmission band characteristic viewed from the other input terminal. It is moved in the wavelength direction. In the following description, the bandwidth corresponding to half the channel optical frequency interval is referred to as “reference bandwidth”, and the center wavelength of each transmission band, that is, the wavelengths λ ₁ and λ ₃ in FIG. A wavelength is referred to as a “channel wavelength”, and a band from the shortest wavelength to the longest wavelength used for wavelength multiplexing communication is referred to as a “communication band”.

  If the transmission band characteristic of the interleaver allows the band corresponding to the reference bandwidth centered on each channel wavelength to pass without loss and completely blocks the other bands, the interleaver 1 can be used for communication. It becomes possible to use the entire bandwidth for communication. However, as described in Non-Patent Document 1, in the actual interleaver 1, each transmission bandwidth is about 60% of the reference bandwidth, and about 40% for each channel, communication is performed. There is a problem that can not be used. Note that the transmission band is a band whose insertion loss is within 0.5 dB with respect to the minimum value of the insertion loss of the interleaver 1, more specifically, when the minimum loss is x (dB), the loss is x + 0. The bandwidth is within 5 (dB).

  SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an optical multiplexing apparatus and method that solves the above-described problems and reduces the band that cannot be used for communication within the communication band as much as possible.

According to the optical multiplexing device of the present invention,
1st to Nth optical interleavers (N is an integer of 2 or more) and an optical coupler for multiplexing the output signals of the 1st to Nth optical interleavers, and within the band used for communication, An optical interleaver whose transmission band is a stop band of K optical interleavers (K is an integer from 1 to N) is present in the first to Nth optical interleavers.

According to another embodiment of the optical multiplexing device of the present invention,
It is preferable that the ratio of each transmission bandwidth of each optical interleaver to the channel optical frequency interval is not less than 1 / 2N and less than 1. Further, the channel optical frequency interval of each optical interleaver is the same, and it is preferable that the transmission band characteristics of each optical interleaver are sequentially shifted in the wavelength direction by 1 / 2N of the channel optical frequency interval, particularly when N = 2. Preferably there is. Here, the transmission band is preferably a band whose loss is within 0.5 dB with respect to the minimum loss of the optical interleaver.

According to the optical multiplexing method of the present invention,
Each of the first to Nth optical interleavers (N is an integer of 2 or more) performs optical interleaving, outputs the first to Nth optical signals, and the first to Nth optical signals are output by the optical coupler. An optical interleaver whose transmission band is a stop band of a Kth optical interleaver (K is an integer from 1 to N) within a band used for communication. It exists in the Nth optical interleaver.

  The transmission band characteristics of each optical interleaver are shifted so that no band is blocked by all optical interleavers within the band used for communication, and the output optical signal of each optical interleaver is independent of wavelength. Bands that cannot be used can be reduced by multiplexing with an optical coupler.

  The best mode for carrying out the present invention will be described in detail below with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of an optical multiplexing apparatus 1 according to the present invention. FIG. 1 shows only the portions necessary for explaining the present invention. As shown in FIG. 1, the optical multiplexing apparatus 1 includes AWGs 21 to 24, optical interleavers 11 and 12, and an optical coupler 3.

The AWG 21 multiplexes optical signals having three wavelengths λ ₁ , λ _5, and λ ₉ , the AWG 22 multiplexes optical signals having _three wavelengths λ ₃ , λ _7, and λ ₁₁ , and the interleaver 11 The optical signals multiplexed by the AWG 21 and AWG 22 are interleaved and output. Similarly, the AWG 23 multiplexes optical signals with three wavelengths λ ₂ , λ _6, and λ ₁₀ , and the AWG 24 multiplexes optical signals with three wavelengths λ ₄ , λ _8, and λ ₁₂ to generate an interleaver. 12 interleaves and outputs the optical signals multiplexed by the AWG 23 and the AWG 24. The wavelength is shorter as the subscript number is smaller.

  FIG. 2 is a diagram illustrating the transmission band characteristics of the interleavers 11 and 12, where the upper stage is the characteristics of the interleaver 11 and the lower stage is the characteristics of the interleaver 12. The upper solid line is the transmission band characteristic seen from the input terminal connected to the AWG 21, the upper dotted line is the transmission band characteristic seen from the input terminal connected to the AWG 22, and the lower solid line is to the AWG 23. It is a transmission band characteristic seen from the connected input terminal, and the lower dotted line is the transmission band characteristic seen from the input terminal connected to the AWG 24.

  The transmission band characteristic of the interleaver 11 shown in the upper part of FIG. 2 is the same as that shown in FIG. 6, and the transmission band characteristic of the interleaver 12 shown in the lower part of FIG. Only half of the width is shifted in the wavelength direction.

As is clear from FIG. 2, the interleaver 12 passes through a portion where both the transmission band characteristics indicated by the solid line and the dotted line of the interleaver 11 drop, that is, an intermediate region between λ _2n−1 and λ _{2n + 1} (n is an integer). The interleaver 11 passes a portion where both the transmission band characteristics indicated by the solid line and the dotted line of the interleaver 12 fall, that is, an intermediate region between λ _2n and λ _{2n + 2} (n is an integer).

  The coupler 3 combines the outputs of the interleavers 11 and 12 to output an optical signal having the spectrum shown in FIG. In the present invention, the outputs of the interleavers 11 and 12 whose transmission band characteristics are shifted from each other are multiplexed by the coupler 3 whose transmission band characteristics do not depend on the wavelength, so that, as shown in FIG. The bandwidth that cannot be used for communication can be reduced.

  For example, since an optical OFDM signal modulated by optical orthogonal frequency multiplexing (OFDM) technology has a rectangular optical spectrum, when an optical OFDM signal is used as an optical signal of each wavelength shown in FIG. There is an advantage that almost the entire band can be used for information transmission.

  Although the above-described embodiment uses two interleavers, a configuration using three or more interleavers may be used. For example, when N interleavers are used, the ratio of the transmission bandwidth of each interleaver to the reference bandwidth is 1 / N or more and less than 1, so that an interleaver having a stopband of a certain interleaver as a transmission band can be obtained. It can be made to exist. In addition, it is preferable that the ratio of each transmission bandwidth of each interleaver to the reference bandwidth is the same, and the value is as small as possible.

  More simply, an interleaver having the same channel optical frequency interval and having the transmission band characteristics of each interleaver sequentially shifted in the wavelength direction by 1 / N of the reference bandwidth may be used. Further, the coupler 3 is not an input with 2 inputs and an output but an output with N inputs and an output. However, since the output from each interleaver becomes 1 / N due to the loss in the coupler with N inputs and 1 output, the number of interleavers is preferably two as shown in the embodiment. In this case, the loss in the coupler is It can be suppressed to 3 dB, which is sufficiently acceptable.

It is a schematic block diagram of the optical multiplexing apparatus by this invention. It is a figure which shows the transmission band characteristic of both interleavers. It is a figure which shows the spectrum of the optical signal which a coupler outputs. It is a block diagram of the optical multiplexing apparatus by a prior art. It is a figure which shows the spectrum of the optical signal which each part of the optical multiplexing apparatus by a prior art outputs. It is a figure which shows the transmission band characteristic of an interleaver.

Explanation of symbols

1, 11, 12 Optical interleaver 21, 22, 23, 24 AWG
3 Optical coupler

Claims (6)

1st to Nth optical interleavers, where N is an integer greater than or equal to 2,
An optical coupler for multiplexing the output signals of the first to Nth optical interleavers;
With
When K is an integer from 1 to N, an optical interleaver whose transmission band is the stop band of the Kth optical interleaver is included in the first to Nth optical interleavers within the band used for communication. Exists,
Optical multiplexer. The ratio of each transmission bandwidth of each optical interleaver to the channel optical frequency interval is not less than 1 / 2N and less than 1.
The optical multiplexing device according to claim 1. The channel optical frequency interval of each optical interleaver is the same,
The transmission band characteristics of each optical interleaver are sequentially shifted in the wavelength direction by 1 / 2N of the channel optical frequency interval.
The optical multiplexing apparatus according to claim 1 or 2.   The optical multiplexing device according to any one of claims 1 to 3, wherein N is two. The transmission band is a band whose loss is within 0.5 dB with respect to the minimum loss of the optical interleaver.
The optical multiplexing device according to any one of claims 1 to 4. First to Nth optical interleavers, where N is an integer equal to or greater than 2, and performing optical interleaving and outputting first to Nth optical signals;
Combining the first to Nth optical signals by an optical coupler;
With
When K is an integer from 1 to N, an optical interleaver whose transmission band is the stop band of the Kth optical interleaver is included in the first to Nth optical interleavers within the band used for communication. Exists,
Optical multiplexing method.

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