JP2006314001A - Decoder for optical encoding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a decoder capable of sending an encoded optical signal to a following stage as it is without any influence of decoding operation. <P>SOLUTION: Provided is the decoder for optical encoding which puts an optical signal decoded through first decoding operation back into an input optical encoded signal through second decoding operation by a grating waveguide for decoding where a plurality of diffraction gratings having different reflection wavelengths are formed in a guide direction of an optical waveguide, by a means of receiving the encoded optical signal from one end portion of the grating waveguide, and by a means of making reflected light from the grating waveguide incident on the grating waveguide again from the other end portion. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical encoder, an optical decoder, an optical code division multiplexing communication apparatus, and the like used for optical code division multiplexing (OCDMA).

  In recent years, in optical fiber communication, an optical encoding multiplexing method has attracted attention as a method other than time division multiplexing (TDM) and wavelength division multiplexing (WDM). In this optical code division multiplexing, for example, an optical pulse is transmitted through a diffraction grating, an optical waveguide, an optical fiber grating, etc., and is encoded (encoded) into various patterns and transmitted, and decoded on the receiving side. Then, the operation of returning to the pulse shape is performed by taking the optical correlation.

  In optical code division multiplexing, in a method called Frequency-Hopping method, encoding is performed by selecting a specific wavelength and giving a delay to each by a fiber grating, and similarly giving a reverse pattern delay to each by a fiber grating. There is something to decrypt.

The followings have been reported for the prior art as a configuration for providing such encoding and decoding. (For example, refer to Patent Document 1.) FIG. 4 shows a configuration example of the encoding / decoding device 30. The encoding / decoding device 30 includes an encoder 11 and a decoder 21 and also functions as an optical communication device. For example, in the encoding / decoding device 30, the optical pulse generator 31 generates an optical RZ signal having a data rate of 2.5 Gps with an optical pulse half width of 24 ps. The generated optical RZ signal is input to an encoder (encoder) E (Ma) 11 via an optical circulator 15A. The encoder 11 encodes the input optical RZ signal according to the M sequence code Ma. The optical signal waveform Pi input to the encoder 11 and the encoded signal waveform Pe from the encoder 11 are shown in FIGS. 5 (a) and 5 (b), respectively. It can be seen that an encoded signal waveform (optical pulse train) Pe having a spreading time of about 360 ps and a period of 2.5 Gps is obtained. The encoded optical pulse train Pe is amplified by the optical amplifier 18 and then input to the decoder (decoder) D (Ma) 21 via the optical circulator 17. As described above, the decoder 21 is configured to decode the encoded signal using the M-sequence code M a. The decoded optical signal from the decoder 21 is received by a light receiver (optical detector) 32 and converted into a decoded electric signal. FIG. 5C shows the experimental results for the decoded signal waveform Pd from the decoder 21. It can be seen that a sufficiently practical decoded waveform can be obtained.
JP 2004-170733 A

  However, the decoder having the above-described configuration has a configuration in which a (code) made of a grating is written on a single fiber combined with an optical circulator. Therefore, in a conventional optical code decoder, if the code does not match, it is newly encoded by the decoding operation, so that it cannot be sent to the subsequent stage in its original state. It was.

  The present invention solves the above-mentioned problems of the prior art, and when the codes (codes) obtained by the decoding of the encoding / decoding device do not match, the encoding is first performed without the influence of the decoding operation. A decoder capable of sending an optical signal as it is to a subsequent stage is provided.

  In order to solve the above-described problems, the first configuration of the present invention includes a decoding grating waveguide in which a plurality of diffraction gratings having different reflection wavelengths are formed in the waveguide direction of the optical waveguide, and the grating waveguide. Means for entering the encoded optical signal from one end, and means for making the reflected light from the grating waveguide again enter the grating waveguide from the other end.

  According to the first configuration of the present invention, it is possible to provide an optical encoding decoder that returns an optical signal decoded by a first decoding operation to an input optical encoded signal by a second decoding operation. Have.

  In the second configuration of the present invention, one end of the grating waveguide is connected to the second port of the first optical circulator, and the other end is connected to the second port of the second optical circulator. To do.

  According to the second configuration of the present invention, the optical signal decoded by the first decoding operation is returned to the input optical encoded signal by the second decoding operation using a simple component configuration. The decoder can be provided.

  In the third configuration of the present invention, a plurality of optical encoding / decoding devices are connected in cascade.

  According to the third configuration of the present invention, an optical encoding decoder capable of repeatedly performing an operation of sending a decoded signal to a subsequent stage in an original state can be provided.

  The optical encoding decoder of the present invention includes a decoding grating waveguide in which a plurality of diffraction gratings having different reflection wavelengths are formed in the waveguide direction of the optical waveguide, and encoded light from one end of the grating waveguide. The optical signal decoded by the first decoding operation by means of a configuration having means for injecting the signal and means for injecting the reflected light from the grating waveguide into the grating waveguide again from the other end, There is an effect that it is possible to provide an optical encoding decoder that returns to an input optical encoded signal by a second decoding operation.

  Further, in the case of a configuration in which one end of the grating waveguide is connected to the second port of the first optical circulator and the other end is connected to the second port of the second optical circulator, Using the component configuration, it is possible to provide an optical encoding decoder that returns an optical signal decoded by a first decoding operation to an input optical encoded signal by a second decoding operation.

  In addition, the configuration in which a plurality of optical encoding decoders are connected in cascade has an effect that it is possible to provide an optical encoding decoder that can repeatedly perform an operation of sending a decoded signal to a subsequent stage in its original state.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
The optical encoding decoder according to the first embodiment of the present invention will be described with reference to FIGS.

  The optical encoding decoder according to the first embodiment includes the encoded signal light 101, the first optical circulator 102, the optical fiber 103, the decoding fiber grating 104, the fiber gratings FG1 105, FG2 106, FG3 107, and second. The optical circulator 108, the light receiver 109, and the signal light 110 sent to the decoder at the next stage. The decoding fiber grating 104 has a configuration in which three fiber gratings FG1 105, FG2 106, and FG3 107 having different reflection wavelengths are linearly arranged. The signal light 101 is a first optical circulator 102 and an optical fiber 103. Then, the light enters the decoding fiber grating 104. The signal light reflected by the decoding fiber grating 104 is separated into one that enters the decoding fiber grating 104 again from the opposite direction through the second optical circulator 108 and one that enters the light receiver 109. In the former case, the signal light reflected by the decoding fiber grating 104 becomes the signal light 110 sent to the next stage decoder through the second optical circulator 108. On the other hand, the latter is converted into a decoded electric signal.

  Next, the function of the optical encoding decoder will be described with reference to FIG. The encoded optical signal 101 enters the decoding fiber grating 104 as light # 1 through the optical circulator 102. Decoding operation is performed according to the delay amount determined by the reflection wavelength and position of FG1 105, FG2 106, and FG3 107, and light # 1 is converted to light # 2. Light # 2 passes through the optical circulator 102 and is separated into one going to the second optical circulator and one going to the light receiver. Here, when a correct decoding operation (use of a decoding fiber grating corresponding to the encoder used) is performed on the encoded signal light, it is processed as a decoded electric signal by the light receiver. That's fine. If the correct decoding operation is not performed, the light # 3 that has passed through the optical circulator 102 enters the decoding fiber grating 104, and the decoding operation is performed, so that the light # 3 is converted into the light # 4. Is done. Here, since the light # 3 is incident on the decoding fiber grating 104 composed of FG1 105, FG2 106, and FG3 107 from the opposite direction to the light # 1, the pattern in which the delay amount with respect to the reflected wavelength is reversed. Is given. Therefore, the light # 4 is subjected to the encoding (decoding) operation twice with respect to the light # 1, and the same delay amount is given by the two operations given for each wavelength. As a result, the time waveforms of the light # 4 and the light # 1 are the same. That is, the same time waveform is obtained for the encoded optical signal 101 and the signal light 110 sent to the next stage decoder.

  In the present embodiment, the number of individual fiber gratings in the decoding fiber grating constituting the optical encoding decoder is three, but the number can be given appropriately. In addition, although two three-terminal elements are used as the optical circulator, it is obvious that the same function can be obtained with one optical circulator if a four-terminal optical circulator is used.

(Embodiment 2)
Next, the optical encoding decoder according to the second embodiment will be described with reference to FIG. The optical encoding decoder according to the second embodiment includes an encoded signal light 301, a first optical circulator 302, an optical fiber 303, a decoding fiber grating 304, a second optical circulator 305, a light receiver 1 306, and a decoding. Fiber grating 2 307, light receiver 2 308, decoding fiber grating n 309, light receiver n 310, and signal light 311 sent to the next stage decoder. The series of decoding fiber gratings 304, 307, and 309 has a configuration in which three fiber gratings having different reflection wavelengths are linearly arranged. The signal light 301 passes through the first optical circulator 302 and the optical fiber 303. Then, the light enters the decoding fiber grating 1304. The signal light reflected by the decoding fiber grating 1 304 passes through the second optical circulator 305 and is separated into one that enters the decoding fiber grating 1 304 again from the opposite direction and one that enters the light receiver 306. The former is reflected by the decoding fiber grating 1304 and sent to the next decoder through the second optical circulator 305. On the other hand, the latter is converted into a decoded electric signal.

  A series of decoding fiber gratings 304, 307, and 309 may be the same or different, and various encoding (decoding) patterns can be obtained by arbitrarily setting the number of fiber gratings, the reflection wavelength, and the delay amount. Can do.

  The function of the optical encoding decoder is the same as that described in the first embodiment. By connecting the decoders in cascade, the operation of sending the decoded signal to the subsequent stage can be repeated, and even if a plurality of operations are repeated, the encoded optical signal 301 is sent to the next stage decoder. The same time waveform as that of the signal light 310 is obtained.

  In the present embodiment, the number of individual fiber gratings in the decoding fiber grating constituting the optical encoding decoder is three, but the number can be given appropriately. Further, although 2n three-terminal elements are used as the optical circulator, it is obvious that the same function can be obtained if n four-terminal optical circulators are used.

  An optical encoding decoder according to the present invention includes a decoding grating waveguide in which a plurality of diffraction gratings having different reflection wavelengths are formed in the waveguide direction of an optical waveguide, and encoding from one end of the grating waveguide. The optical signal decoded by the first decoding operation can be obtained by a configuration having means for injecting an optical signal and means for injecting reflected light from the grating waveguide into the grating waveguide again from the other end. Since it has a mechanism for returning to the input optical encoded signal by the second decoding operation, it is useful as an optical encoding decoder.

1 is a configuration diagram of an optical encoding decoder according to a first embodiment of the present invention. Schematic which shows the function of the decoder for optical encoding in the 1st Embodiment of this invention The block diagram of the decoder for optical encoding in the 2nd Embodiment of this invention Block diagram showing a configuration of an encoding / decoding device in a conventional optical encoding device The figure which shows the experimental result about the optical signal waveform Pi input into the encoder in the conventional optical encoding apparatus, the encoding signal waveform Pe from an encoder, and the decoding signal waveform Pd from a decoder.

Explanation of symbols

101 encoded signal light 102 first optical circulator 103 optical fiber 104 fiber grating for decoding 105 fiber grating FG1
106 FG2
107 FG3
DESCRIPTION OF SYMBOLS 108 2nd optical circulator 109 Light receiver 110 Signal light sent to the next decoder 301 Encoded signal light 302 First optical circulator 303 Optical fiber 304 Decoding fiber grating 1
305 Second optical circulator 306 Light receiver 1
307 Decoding fiber grating 2
308 Receiver 2
309 Decoding fiber grating n
310 Receiver n
311 Signal light sent to next stage decoder 11, 11A-11H Optical encoder 12, 12A-12H, 13, 13A-13H Optical attenuator 15, 15A-15H, 17, 17A-17H Optical circulator 18 Optical amplifier 19 , 37, 37A Optical fiber 21, 21A-21H Optical decoder 31, 31A-31H Optical pulse generator 32, 32A-32H Optical detector 33, 39 Optical coupler 41, 41B-41H Delay device

Claims (3)

An apparatus for decoding an optically encoded signal generated by giving a time delay for each specific wavelength component,
A grating grating for decoding in which a plurality of diffraction gratings having different reflection wavelengths are formed in the waveguide direction of the optical waveguide, means for entering an encoded optical signal from one end of the grating waveguide, and a grating waveguide Means for re-injecting the reflected light from the other end into the grating waveguide, and the optical signal decoded by the first decoding operation is converted into the input optical encoded signal by the second decoding operation. An optical encoding decoder, wherein 2. The grating waveguide according to claim 1, wherein one end of the grating waveguide is connected to the second port of the first optical circulator, and the other end is connected to the second port of the second optical circulator. Decoder for optical encoding. 2. The optical encoding decoder according to claim 1, wherein a plurality of optical encoding decoders are connected in cascade.

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