JP2006074557A - Optical communication system and method, optical multi-communication system and method, and optical receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical multi-communication system and its method which can eliminating a disturbance optical signal at the previous stage of a photodetector and realizes optical transmission with no mutual interference between the existing optical communication system and an added optical communication system of an optical CDM (code division multiplex) method. <P>SOLUTION: This optical multi-communication system has a first optical transmitter for transmitting an optical signal for communication of an optical CDM method, a second optical transmitter for transmitting an optical signal for communication different from the optical signal for communication, a first optical receiver for receiving the optical signal for communication transmitted from the first optical transmitter, and a second optical receiver for receiving the other optical signal for communication transmitted from the second optical transmitter. The first optical receiver is provided with a disturbance optical signal eliminator for branching the optical signal received by the first optical receiver into two optical signals or more, providing prescribed optical path length difference, combining the optical signals and outputting the combined optical signals at prescribed light intensity, and a photodetector for detecting the optical signals output from the disturbance optical signal eliminator. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical CDM (Code Division Multiplex) optical communication system, an optical multiplex communication system, an optical communication method, an optical multiplex communication method, and an optical reception device that transmit and receive an optical signal encoded by an optical transmission device.

An optical CDM system is promising as a method for newly adding an optical communication system to an existing optical communication system without affecting the existing optical communication system (for example, see Non-Patent Document 1). In the optical CDM system, since an optical signal is spread over a wide optical frequency width, it is possible to communicate with an optical signal having a weak intensity that does not affect the existing optical communication system due to the coding gain. is there. Here, the intensity level of the optical signal that does not affect the existing optical communication system assumed to have an extinction ratio of 8 to 12 dB is required to be as small as several percent.
Kazuaki Kikuchi, Yuichi Takushima “Spread Spectrum Technology in Optical Fiber Communication” IEICE Tech. SSE 93-141, OCS 93-71 (1994-03)

  However, the optical intensity of the optical signal transmitted in the existing optical communication system is extremely large compared to the optical intensity of the optical signal transmitted in the optical CDM optical communication system to be added. For this reason, for an optical CDM optical communication system, an optical signal transmitted in an existing optical communication system acts as an interference optical signal. Ensuring a sufficient coding gain for such an interfering optical signal requires expansion of the optical frequency bandwidth, and thus is limited by signal waveform deterioration caused by chromatic dispersion in the optical transmission line. Furthermore, the hard limiter for enhancing the saturation and anti-jamming resistance of the optical receiver requires a complicated processing circuit.

  Therefore, in the present invention, an optical transmission without mutual interference between an existing optical communication system and an additional optical CDM optical communication system can be performed by a simple method so that an interference optical signal can be removed before the photodetector. It is an object of the present invention to provide an optical communication system, an optical multiplex communication system, and an optical receiver that realize the above. Moreover, it aims at providing the method.

  In order to achieve the above object, the present inventors have determined that the frequency bandwidth of an optical signal transmitted in an existing optical communication system is narrower than the optical frequency bandwidth of an optical signal transmitted in an optical CDM optical communication system. The present invention was completed by paying attention to the long coherence length or the wide pulse width.

  Specifically, an optical communication system according to the present invention receives an optical transmitter for transmitting a communication optical signal spread-coded in an optical frequency domain, and receives the optical signal for communication transmitted from the optical transmitter. An optical communication system comprising: an optical communication device, wherein the optical reception device branches the communication optical signal transmitted from the optical transmission device into two or more optical frequency bandwidths of the communication optical signal An interference light signal remover that outputs an optical path with a predetermined light intensity by providing an optical path length difference equal to or greater than a value converted into a length, and detecting the communication optical signal output from the interference light signal remover And a photodetector. Here, “the value obtained by converting the optical frequency bandwidth of the optical signal for communication into a length” is, for example, converted by the following formula 1 in the case of a Mach-Zehnder interferometer, Michelson interferometer, and Fabry-Perot interferometer. It shall be. Further, for example, in the case of an AWG (arrayed waveguide diffraction grating), it is converted by the following formula 2.

  An optical communication system according to the present invention includes an optical transmitter that transmits an optical signal for communication that is spread-coded in the optical frequency domain, and an optical receiver that receives the optical signal for communication transmitted from the optical transmitter. And an optical path length equal to or longer than a coherence length of the optical signal for communication by branching the optical signal for communication transmitted from the optical transmitter into two or more. A jamming light signal remover that outputs a predetermined intensity by combining with a difference, and a photodetector that detects the communication optical signal output from the jamming light signal remover. .

  An optical communication system according to the present invention receives an optical transmission device that transmits a communication pulse optical signal that is spread-encoded in an optical frequency domain, and receives the communication pulse optical signal that is transmitted from the optical transmission device. An optical communication system comprising: an optical receiving device, wherein the optical receiving device branches the communication pulse optical signal transmitted from the optical transmission device into two or more, and sets a pulse width of the communication pulse optical signal. An interference light signal eliminator that outputs an optical path with a predetermined light intensity by providing an optical path length difference equal to or greater than a length converted value, and detecting the communication pulse light signal output from the interference light signal eliminator And a photodetector.

  An optical multiplex communication system according to the present invention includes a first optical transmitter that transmits a communication optical signal spread-coded in an optical frequency domain, and an optical frequency band narrower than an optical frequency bandwidth of the communication optical signal. A second optical transmission device that transmits an optical signal for communication having another width, an optical multiplexer that connects the first optical transmission device and the second optical transmission device, and the optical multiplexing from the first optical transmission device. A first optical receiving device that receives the communication optical signal transmitted through the optical receiver, and a second optical receiver that receives the other optical signal for communication transmitted from the second optical transmitting device through the optical multiplexer. An optical multiplex communication system including a two-optical receiver, and an optical demultiplexer that connects the first optical receiver and the second optical receiver, wherein the first optical receiver is the first optical receiver The optical signal received by the optical receiver is divided into two or more optical signals, and the optical signal is transmitted to the branched optical signal. A predetermined light by combining with an optical path length difference that is equal to or greater than the value obtained by converting the optical frequency bandwidth of the optical signal for use into a length and less than the value obtained by converting the optical frequency bandwidth of the other communication optical signal into a length. An interference light signal remover that outputs at an intensity, and a photodetector that detects the optical signal output from the interference light signal remover. Here, the “value obtained by converting the optical frequency bandwidth of the optical signal for communication into the length” is converted according to Equation 1 or Equation 2.

  The optical communication multiplex system according to the present invention includes a first optical transmission device that transmits a communication optical signal that is spread-coded in the optical frequency domain, and a coherence length that is longer than the coherence length of the communication optical signal. A second optical transmitter that transmits another optical signal for communication, an optical multiplexer that connects the first optical transmitter and the second optical transmitter, and the optical multiplexer from the first optical transmitter A first optical receiver that receives the communication optical signal transmitted via the second optical receiver, and a second optical receiver that receives the other optical signal for communication transmitted from the second optical transmitter via the optical multiplexer. An optical multiplex communication system comprising: an optical receiver; and an optical demultiplexer that connects the first optical receiver and the second optical receiver, wherein the first optical receiver includes the first optical receiver. An optical signal received by the receiving device is branched into two or more optical signals, and the coherence length of the optical signal for communication is longer than An interference optical signal remover that outputs an optical signal with a predetermined light intensity by providing an optical path length difference equal to or less than the coherence length of the other communication optical signal, and the optical signal output from the interference optical signal remover. And a photodetector for detection.

  The optical communication multiplex system according to the present invention includes a first optical transmission device that transmits a communication pulse optical signal that is spread-encoded in an optical frequency domain, and a pulse width that is larger than a pulse width of the communication pulse optical signal. A second optical transmitter that transmits another optical pulse signal for communication, an optical multiplexer that connects the first optical transmitter and the second optical transmitter, and the optical multiplexer from the first optical transmitter A first optical receiving device that receives the communication pulse optical signal transmitted through the optical receiver, and a second communication pulse optical signal transmitted from the second optical transmission device through the optical multiplexer. And an optical demultiplexer that connects the first optical receiver and the second optical receiver, wherein the first optical receiver includes the first optical receiver and the optical demultiplexer that connects the first optical receiver and the second optical receiver. The pulse optical signal received by the first optical receiver is converted into two or more optical signals. An optical path length difference equal to or greater than a value obtained by converting the pulse width of the communication pulse optical signal into a length and equal to or less than a value obtained by converting the pulse width of the other communication pulse optical signal into a length is combined to be predetermined. The interference light signal eliminator that outputs the light with the light intensity and the photodetector that detects the pulsed light signal output from the interference light signal eliminator.

  The optical communication multiplex system according to the present invention includes a first optical transmitter that transmits a communication optical signal spread-coded in an optical frequency domain, and an optical frequency narrower than an optical frequency bandwidth of the communication optical signal. A second optical transmission device that transmits another optical signal for communication of bandwidth, an optical multiplexer that connects the first optical transmission device and the second optical transmission device, and the optical multiplexing device from the first optical transmission device. A first optical receiver for receiving the communication optical signal transmitted via a wave multiplier; and the optical multiplexer and the first optical receiver connected to the first optical receiver from the second optical transmitter A second optical receiving device that receives the other optical signal for communication transmitted via the optical communication system, wherein the first optical receiving device receives the first optical receiving device. The optical signal for communication is converted into a branched optical signal obtained by branching an optical signal into two or more optical signals. An optical path length difference equal to or greater than a value obtained by converting a frequency bandwidth into a length and less than or equal to a value obtained by converting an optical frequency bandwidth of the other communication optical signal into a length is provided, and the branched light provided with the optical path length difference A disturbing light signal remover for combining and branching signals, outputting one of the signals to the first optical receiver with a predetermined light intensity, and outputting the other toward the second optical receiver; and the disturbing light A photodetector that detects the optical signal output from the signal remover to the inside of the first optical receiver. Here, the “value obtained by converting the optical frequency bandwidth of the optical signal for communication into the length” is converted according to Equation 1 or Equation 2.

  The optical communication multiplex system according to the present invention includes a first optical transmission device that transmits a communication optical signal that is spread-coded in the optical frequency domain, and a coherence length that is longer than the coherence length of the communication optical signal. A second optical transmitter that transmits another optical signal for communication, an optical multiplexer that connects the first optical transmitter and the second optical transmitter, and the optical multiplexer from the first optical transmitter A first optical receiver that receives the communication optical signal transmitted via the first optical receiver, and the second optical transmitter connected to the first optical receiver via the optical multiplexer and the first optical receiver. And a second optical receiving device that receives the other optical signal for communication transmitted in this manner, wherein the first optical receiving device receives the optical signal received by the first optical receiving device. Is equal to or longer than the coherence length of the optical signal for communication to a branched optical signal that is branched into two or more optical signals. An optical path length difference equal to or shorter than the coherence length of the other optical signal for communication is provided, the branched optical signals provided with the optical path length difference are combined and branched, and one of the first optical signals with a predetermined light intensity is provided. An interfering optical signal remover that outputs to the inside of the receiving device and outputs the other to the second optical receiving device, and the optical signal that is output from the interfering optical signal remover to the inside of the first optical receiving device And a photodetector for detecting.

  The optical communication multiplex system according to the present invention includes a first optical transmission device that transmits a communication pulse optical signal that is spread-encoded in an optical frequency domain, and a pulse width that is larger than a pulse width of the communication pulse optical signal. A second optical transmitter that transmits another optical pulse signal for communication, an optical multiplexer that connects the first optical transmitter and the second optical transmitter, and the optical multiplexer from the first optical transmitter A first optical receiver for receiving the communication pulse optical signal transmitted via the optical device; and the optical multiplexer and the first optical receiver connected to the first optical receiver from the second optical transmitter A second optical receiver that receives the other optical pulse signal for communication transmitted via the optical multiplex communication system, wherein the first optical receiver receives the first optical receiver. Branching pulse optical signal into two or more optical signals An optical path length difference equal to or greater than a value obtained by converting the pulse width of the communication pulse light signal into a length and less than a value obtained by converting the pulse width of the other communication pulse light signal into a length is provided in the signal, and the optical path length difference Is coupled to the branched optical signal and branched, and one is output to the inside of the first optical receiver with a predetermined light intensity, and the other is output to the second optical receiver. And a photodetector that detects the pulsed optical signal output from the interfering optical signal remover to the inside of the first optical receiver.

  The optical receiver according to the present invention is an optical receiver that receives a communication optical signal that is spread-encoded in an optical frequency domain, and branches the communication optical signal into two or more, and the communication optical signal. An interference light signal remover that outputs a predetermined optical intensity by providing an optical path length difference equal to or greater than a value obtained by converting the optical frequency bandwidth into a length, and the communication light output from the interference light signal remover And a photodetector for detecting an optical signal. Here, the “value obtained by converting the optical frequency bandwidth of the optical signal for communication into the length” is converted according to Equation 1 or Equation 2.

  The optical receiver according to the present invention is an optical receiver that receives a communication optical signal that is spread-encoded in an optical frequency domain, and branches the communication optical signal into two or more, and the communication optical signal. An interference optical signal eliminator that outputs an optical path with a predetermined intensity by providing an optical path length difference equal to or greater than the coherence length, and a photodetector that detects the communication optical signal output from the interference optical signal eliminator. It is characterized by providing.

  An optical receiving apparatus according to the present invention is an optical receiving apparatus that receives a communication pulse optical signal that is spread-encoded in an optical frequency domain, and branches the communication pulse optical signal into two or more for communication. An interference light signal eliminator that outputs an optical path with a predetermined optical intensity by providing an optical path length difference equal to or greater than a value obtained by converting the pulse width of the pulse optical signal into a length, and the communication output from the interference light signal eliminator And a photodetector for detecting a pulse light signal for use.

  The optical receiver according to the present invention receives a communication optical signal spread-coded in the optical frequency domain and another optical signal for communication having an optical frequency bandwidth narrower than the optical frequency bandwidth of the optical signal for communication. An optical receiving device, wherein the optical signal received by the optical receiving device is branched into two or more optical signals, and the optical frequency bandwidth of the optical signal for communication is converted into a length or more, and An optical path length difference equal to or less than a value obtained by converting the optical frequency bandwidth of another optical signal for communication into a length is provided, and the branched optical signals provided with the optical path length difference are combined and branched, and one of them is divided into predetermined light. An interference light signal remover that outputs the light intensity inside the optical reception device and outputs the other to the outside of the optical reception device; and the light output from the interference light signal removal device to the inside of the optical reception device. And a photodetector for detecting a signal. Here, the “value obtained by converting the optical frequency bandwidth of the optical signal for communication into the length” is converted according to Equation 1 or Equation 2.

  The optical receiving apparatus according to the present invention also includes a communication optical signal that is spread-coded in the optical frequency domain and a light that receives another communication optical signal having a coherence length longer than the coherence length of the communication optical signal. A receiving device, wherein the optical signal received by the optical receiving device is branched into two or more optical signals, and the coherence length of the other optical signal for communication is greater than the coherence length of the optical signal for communication. The following optical path length difference is provided, the branched optical signals provided with the optical path length difference are combined and branched, one is output to the inside of the optical receiver at a predetermined light intensity, and the other is the optical receiver An interference light signal remover that outputs to the outside of the device, and a photodetector that detects the optical signal output from the interference light signal remover to the inside of the optical receiver.

  The optical receiver according to the present invention receives a communication pulse optical signal spread-encoded in the optical frequency domain and another communication pulse optical signal having a pulse width wider than the pulse width of the communication pulse optical signal. An optical receiver, wherein the pulse optical signal received by the optical receiver is branched into two or more optical signals, and is equal to or greater than a value obtained by converting the pulse width of the communication pulse optical signal into a length. An optical path length difference equal to or smaller than a value obtained by converting the pulse width of the communication pulse optical signal into a length is provided, the branched optical signals provided with the optical path length difference are combined and branched, and one of them is combined to obtain a predetermined An interference light signal remover that outputs the light intensity to the inside of the optical reception device and outputs the other to the outside of the optical reception device, and the interference light signal remover that is output to the inside of the optical reception device. A photodetector for detecting a pulsed optical signal; It is characterized in.

  The optical communication method according to the present invention is an optical communication method for transmitting and receiving a communication optical signal spread-coded in the optical frequency domain between an optical transmission device and an optical reception device, wherein the optical reception device comprises: The optical signal for communication transmitted from the optical transmitter is branched into two or more, and the optical frequency bandwidth of the optical signal for communication is provided with an optical path length difference equal to or greater than the value converted into a length to be combined with a predetermined value. It detects after making it light intensity, It is characterized by the above-mentioned. Here, the “value obtained by converting the optical frequency bandwidth of the optical signal for communication into the length” is converted according to Equation 1 or Equation 2.

  The optical communication method according to the present invention is an optical communication method for transmitting and receiving a communication optical signal spread-coded in the optical frequency domain between an optical transmission device and an optical reception device, wherein the optical reception device comprises: Detecting after the optical signal for communication transmitted from the optical transmission device is branched into two or more and combined with an optical path length difference equal to or greater than the coherence length of the optical signal for communication to obtain a predetermined intensity. Features.

  The optical communication method according to the present invention is an optical communication method for transmitting and receiving a communication pulse optical signal spread-encoded in an optical frequency domain between an optical transmitter and an optical receiver, the optical receiver The optical pulse transmission signal transmitted from the optical transmitter is branched into two or more, and the optical pulse length difference equal to or greater than the value obtained by converting the pulse width of the communication optical pulse signal into a length is combined and combined. It detects after making it the light intensity of this.

  The optical multiplex communication method according to the present invention transmits / receives a communication optical signal spread-coded in the optical frequency domain between an optical transmission device and an optical reception device via an optical transmission line, and transmits the communication optical signal. An optical multiplex communication method for transmitting and receiving another optical signal for communication in an optical frequency band narrower than the optical frequency band of a signal between another optical transmitter and another optical receiver via the optical transmission path, The optical receiver has a branch optical signal obtained by branching an optical signal received by the optical receiver into two or more optical signals, and the optical frequency bandwidth of the communication optical signal is equal to or more than a value converted into a length. It is characterized in that detection is performed after providing an optical path length difference equal to or less than a value obtained by converting the optical frequency bandwidth of the optical signal for communication into a length and combining them to obtain a predetermined light intensity. Here, the “value obtained by converting the optical frequency bandwidth of the optical signal for communication into the length” is converted according to Equation 1 or Equation 2.

  The optical multiplex communication method according to the present invention transmits / receives a communication optical signal spread-coded in the optical frequency domain between an optical transmission device and an optical reception device via an optical transmission line, and transmits the communication optical signal. An optical multiplex communication method for transmitting and receiving another optical signal for communication having a coherence length longer than the coherence length of a signal between another optical transmission device and another optical reception device via the optical transmission path, The optical receiving device branches an optical signal received by the optical receiving device into two or more optical signals, and has an optical path length that is not less than the coherence length of the communication optical signal and not more than the coherence length of the other communication optical signal. Detection is performed after a difference is provided and combined to obtain a predetermined light intensity.

  Also, the optical multiplex communication method according to the present invention transmits / receives a communication pulse optical signal, which is spread-coded in the optical frequency domain, between an optical transmission device and an optical reception device via an optical transmission line. An optical multiplex communication method for transmitting and receiving another optical pulse signal for communication having a wider pulse width than that of an optical signal between another optical transmission device and another optical reception device via the optical transmission path, The optical receiving device branches the pulse optical signal received by the optical receiving device into two or more pulse optical signals, and has a value equal to or greater than a value obtained by converting the pulse width of the communication pulse optical signal into a length, and the other communication pulse. An optical path length difference equal to or less than a value obtained by converting a pulse width of an optical signal into a length is provided and combined to obtain a predetermined light intensity, and then detected.

  The optical multiplex communication method according to the present invention transmits / receives a communication optical signal spread-coded in the optical frequency domain between an optical transmission device and an optical reception device via an optical transmission line, and transmits the communication optical signal. An optical multiplex communication method for transmitting and receiving another optical signal for communication having an optical frequency bandwidth narrower than the optical frequency bandwidth of a signal between another optical transmission device and another optical reception device via the optical transmission line. The optical receiving device is equal to or more than a value obtained by converting the optical frequency bandwidth of the communication optical signal into a length to a branched optical signal obtained by branching an optical signal received by the optical receiving device into two or more optical signals. An optical path length difference equal to or less than a value obtained by converting the optical frequency bandwidth of another optical signal for communication into a length is provided, and the branched optical signals provided with the optical path length difference are combined and branched, and one of them is divided into predetermined light. It is detected after the intensity is increased and the other is output to the other optical receiver. To. Here, the “value obtained by converting the optical frequency bandwidth of the optical signal for communication into the length” is converted according to Equation 1 or Equation 2.

  The optical multiplex communication method according to the present invention transmits / receives a communication optical signal spread-coded in the optical frequency domain between an optical transmission device and an optical reception device via an optical transmission line, and transmits the communication optical signal. An optical multiplex communication method for transmitting and receiving another optical signal for communication having a coherence length longer than the coherence length of a signal between another optical transmission device and another optical reception device via the optical transmission path, The optical receiving device branches an optical signal received by the optical receiving device into two or more optical signals, and the branched optical signal is longer than a coherence length of the communication optical signal and the other optical signal for communication. An optical path length difference equal to or shorter than the coherence length is provided, the branched optical signals provided with the optical path length difference are combined and branched, one of them is set to a predetermined light intensity, and the other is detected as another optical receiver. The output is directed to.

  Also, the optical multiplex communication method according to the present invention transmits / receives a communication pulse optical signal, which is spread-coded in the optical frequency domain, between an optical transmission device and an optical reception device via an optical transmission line. An optical multiplex communication method for transmitting and receiving another communication pulse optical signal having a wider pulse width than a pulse optical signal between another optical transmission device and another optical reception device via the optical transmission line. The optical receiver branches the pulse optical signal received by the optical receiver into two or more pulse optical signals, and the branched optical signal is a value obtained by converting the pulse width of the communication pulse optical signal into a length. An optical path length difference equal to or less than the value obtained by converting the pulse width of the other communication optical pulse signal into a length is provided, the branched optical signals provided with the optical path length difference are combined and branched, and one of them is predetermined. The other light receiving device is detected after the other light intensity is detected. And outputs toward the.

  According to the optical communication system and the optical communication method of the present invention, the interference light signal can be removed at the front stage of the photodetector with a simple configuration, and high communication accuracy can be obtained.

  Further, according to the optical multiplex communication system and the optical multiplex communication method of the present invention, optical transmission without mutual interference between the existing optical communication system and the additional optical CDM optical communication system is realized with a simple configuration. can do. Furthermore, even if the existing optical communication system and the additional CDM optical communication system have the same frequency, communication in both systems is possible, and the same optical frequency (wavelength) multiplex communication can be realized.

  Also, according to the optical receiver of the present invention, in a CDM optical communication system, the interference optical signal can be removed at the front stage of the photodetector with a simple configuration, and high communication accuracy can be obtained. Further, even if added to an existing optical communication system, optical transmission without mutual interference between the existing optical communication system and the additional optical CDM optical communication system can be realized. Furthermore, even if the existing optical communication system and the additional CDM optical communication system have the same frequency, both systems can communicate simultaneously, and the same optical frequency (wavelength) multiplex communication can be realized.

Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiment described below is an example of the configuration of the present invention, and the present invention is not limited to the following embodiment.
(First embodiment)

  FIG. 1 shows a schematic configuration diagram of an optical communication system according to the present embodiment. An optical communication system 100 illustrated in FIG. 1 includes an optical transmission device 10 that transmits a communication optical signal 70c that is spread-coded in the optical frequency domain, and an optical signal that receives the communication optical signal 70c transmitted from the optical transmission device 10. Receiving device 20.

  In the present embodiment, the optical transmitter 10 includes a light source 11 that outputs an optical signal 70a, and an optical modulator that modulates the optical signal 70a output from the light source 11 based on a communication signal 60a and outputs a modulated optical signal 70b. 12 and an optical encoder 14 that spread-codes the modulated optical signal 70b output from the optical modulator 12 in the optical frequency domain and outputs a communication optical signal 70c.

Here, the optical signal 70a output from the light source 11 may have a wide optical frequency bandwidth in order to obtain a sufficient coding gain. For example, SLD (Super Luminescent Diode), ASE (Amplitude Spontaneous)
A light source that outputs non-coherent light such as Emission) can be applied. When the optical signal 70a output from the light source 11 is a pulsed optical signal, it is preferable that the optical signal 70a is a short pulsed optical signal with a short pulse width. By making the optical signal 70a output from the light source 11 an optical signal having a wide optical frequency bandwidth or a short pulse optical signal, it is possible to obtain a high coding gain and a high removal effect of the interfering optical signal.

  As the optical modulator 12, for example, an optical modulator such as an optical frequency modulator, an optical intensity modulator, and an optical phase modulator can be applied according to the communication method of the optical communication system 100.

  The optical encoder 14 performs spread coding on the optical signal for communication 70b by the optical CDM communication method. For example, the baseband signal may be spread-coded by directly multiplying the modulated optical signal 70b output from the optical modulator 12 with a code such as an M-sequence code or Gold sequence code, or output from the optical modulator. The modulated optical signal 70b may be passed through a frequency filter, and the frequency band of the modulated optical signal may be divided and spread encoded. For example, a Mach-Zehnder interferometer can be applied.

  In the present embodiment, one light source 11 is provided, but a plurality of light sources having different optical frequencies of optical signals to be output may be provided. By using a plurality of light sources, optical frequency (wavelength) multiplex communication is enabled. Further, it may be a light source that outputs a single optical signal or a plurality of optical signals whose optical frequency characteristics of light intensity correspond to codes. Further, the light source may directly modulate and output an optical signal. By making the light source, the optical modulator, and the optical encoder into one device, the optical transmitter 10 can be made compact.

  In the present embodiment, the optical receiver 20 branches the communication optical signal 70d transmitted from the optical transmitter 10 into two or more, combines them with a predetermined optical path length difference, and outputs them with a predetermined light intensity. Interfering optical signal remover 21, optical decoder 22 that decodes communication optical signal 70 e output from interfering optical signal remover 21 with a despreading code, and an optical signal for communication decoded by optical decoder 22 And a photodetector 23 for detecting 70f. In this embodiment, the interfering optical signal remover 21, the optical decoder 22, and the photodetector 23 are arranged in this order. However, the interfering optical signal remover 21 is a front stage of the photodetector 23, It may be in any position.

  The optical decoder 22 applies a predetermined optical decoder corresponding to the optical encoder 14 of the optical transmitter 10. In addition, a predetermined photodetector corresponding to the optical modulator 12 of the optical transmission device 10 is applied as the photodetector 23.

  In the present embodiment, the interfering optical signal remover 21 splits the communication optical signal 70d into two or more and gives interference by giving a predetermined optical path length difference between the optical transmitting device 10 and the optical receiving device 20. For example, the optical multiplexer 65 has a function of removing the interference light signal 70g superimposed on the communication optical signal 70c. In the present embodiment, as the interference light signal 70g, signals that are narrower than the optical frequency bandwidth of the communication optical signal 70c transmitted by the optical transmitter 10 or have a long coherence length are removed. When the communication optical signal 70c is a pulse optical signal, the interference optical signal 70g having a pulse width longer than the pulse width of the communication optical signal 70c transmitted by the optical transmitter 10 is removed. This is because the interference light signal 70g has a stronger light intensity than the optical CDM communication optical signal 70c transmitted by the optical transmitter 10, and has a large influence on the reception of the communication optical signal by the optical receiver 20.

  Here, the optical path length difference is equal to or greater than the value obtained by converting the optical frequency bandwidth of the communication optical signal 70c into a length, or greater than the coherence length of the communication optical signal 70c. When the communication optical signal 70c is a pulse signal, the pulse width of the communication pulse optical signal as the communication optical signal 70c is set to a value converted to a length or more. This will be described later.

  For example, a Mach-Zehnder interferometer can be used as the interfering light signal remover 21. Here, the operation principle of the interfering light signal remover 21 when a Mach-Zehnder interferometer is applied as the interfering light signal remover 21 will be described in detail.

  FIG. 2 shows a schematic configuration diagram of a Mach-Zehnder interferometer as the interfering light signal remover 21. The Mach-Zehnder interferometer 91 shown in FIG. 2 includes two half mirrors 50 and 53, two mirrors 52 and 54, a phase delay unit 51, and a lens 55.

  As the half mirrors 50 and 53, for example, a half mirror having transmittance / reflectance according to light intensity or a half mirror having transmittance / reflectivity according to optical frequency can be applied. The half mirror 50 bifurcates the communication optical signal 70d transmitted from the optical transmitter 10 shown in FIG. 1 into, for example, branched optical signals 80a and 80b having half the light intensity. The half mirror 53 reflects the branched optical signal 80b with half the light intensity and transmits the branched optical signal 80a with the half light intensity. Actually, the half mirror 53 transmits the branched optical signal 80b with half light intensity and reflects the branched optical signal 80a with half light intensity, but the description of these optical signals is omitted for convenience.

  The phase delay unit 51 has a function of shifting the phase of the optical signal that passes therethrough. For example, a medium having a refractive index relatively different from that of the outer region or an optical waveguide having a variable refractive index due to an electro-optic effect can be applied. This phase delay unit 51 can provide a difference in optical path length between the branched optical signals 80a and 80b.

  The lens 55 collects the branched optical signals 80a and 80b on the optical fiber 56 connected to the optical decoder 22 shown in FIG.

  The communication optical signal 70d transmitted from the optical transmission device 10 shown in FIG. One branched optical signal 80 a is reflected by the mirror 54, passes through the half mirror 53, and enters the lens 55. The other branched optical signal 80 b is given a difference in optical path length from the branched optical signal 80 a by the phase delay unit 51, reflected by the mirror 52, further reflected by the half mirror 53, and incident on the lens 55. The lens 55 collects the two branched optical signals 80 a and 80 b on the optical fiber 56. At this time, the refractive index is adjusted by the phase delay unit 51 so that the optical path length difference between the branched optical signals 80a and 80b is equal to or greater than the value obtained by converting the optical frequency bandwidth of the communication optical signal 70c into the length, and half of the interfering optical signal 70g. Assuming that the wavelength is a natural number multiple, the components of the interfering light signal 70g out of the optical signals obtained by collecting the branched optical signals 80a and 80b are weakened.

  Here, when the communication optical signal 70c shown in FIG. 1 is not a pulse optical signal, if the optical frequency of the communication optical signal 70c matches the optical frequency of the interference optical signal 70g, the communication optical signal on which the interference optical signal 70g is superimposed. When 70d is caused to interfere, the center frequency component of the communication optical signal 70c that is originally required is also weakened together with the disturbing optical signal 70g. However, since the optical path length difference is equal to or greater than the value obtained by converting the optical frequency bandwidth of the optical signal for optical communication 70c of the optical CDM system into the length, even if the light intensity of the light at the center frequency is weakened, The light intensity of the intensifying light among the light can ensure the light intensity of the communication optical signal 70e after passing through the Mach-Zehnder interferometer 91 as the interference light signal remover 21. On the other hand, since the interference light signal 70g has a high light intensity, the optical frequency bandwidth is narrow, and the light intensity after passing through the Mach-Zehnder interferometer 91 as the interference light signal remover 21 becomes substantially zero. Therefore, the optical path length difference is not less than a value obtained by converting the optical frequency bandwidth of the communication optical signal 70c into a length. Desirably, the optical frequency bandwidth of the interfering light signal 70g is set to be equal to or less than a value converted into a length. Here, the “value obtained by converting the optical frequency bandwidth of the communication optical signal 70c into a length” is converted by the following Equation 3.

  On the other hand, when the optical path length difference is equal to or greater than the coherence length of the communication optical signal 70c, the communication optical signal 70c does not interfere, and half of the communication optical signal 70c passes through the interfering optical signal remover 21 and is optically decoded. Is input to the device 22. Therefore, in order to output the communication optical signal 70e with a predetermined light intensity, it is desirable that the optical path length difference is not less than the coherence length of the communication optical signal 70c and not more than the coherence length of the interfering light signal 70g. This is because the coherence length decreases as the optical frequency bandwidth increases.

  Further, when the communication optical signal 70c shown in FIG. 1 is a pulsed optical signal, the optical path length difference is set to a value equal to or greater than the value obtained by converting the pulse width of the communication pulsed optical signal as the communication optical signal 70c into a length, and the interference light It is desirable that the pulse width of the signal 70g be equal to or less than the value converted into the length. If the optical path length difference is greater than or equal to the value obtained by converting the pulse width of the communication pulse optical signal into a length, the pulses of the communication pulse optical signal as the communication optical signal 70c do not overlap each other due to the optical path length difference. If the optical path length difference is equal to or less than the value obtained by converting the pulse width of the interfering light signal 70g into a length, the pulses of the interfering optical signal 70g overlap each other due to the optical path length difference, and therefore only the interfering optical signal can be removed by interference. it can. The interference light signal can be removed regardless of whether it is an RZ (Return-To-Zero) signal or an NRZ (Non-Return-To-Zero) signal.

  Further, since the optical intensity of the light output from the Mach-Zehnder interferometer 91 as the interfering optical signal remover 21 becomes a comb-like sine function with respect to the optical frequency, the optical path length difference is the optical encoder shown in FIG. 14 can also be determined in relation to the optical decoder 22. In other words, the period of the sine function that is the light intensity of the light output from the Mach-Zehnder interferometer 91 shown in FIG. 2 only needs to satisfy one of the following conditions.

(A) A natural number of the optical frequency width of the chip constituting each code in the optical encoder 14.
When the code in the optical encoder 14 is a repetition code divided into a plurality of repetition parts,
(B) 2 ^m (m is a natural number) times the optical frequency width of each repeated portion of the repetition code, and 2 ^−k (k is a natural number) times the optical frequency bandwidth of the communication optical signal 70c.

By satisfying one of the conditions (a) and (b) above, the light of the communication optical signal 70 f that has passed through the Mach-Zehnder interferometer 91 as the interfering optical signal remover 21 and has passed through the optical decoder 22. The intensity can be a predetermined light intensity that can be detected by the photodetector. Further, by adding the following conditions to the above conditions (a) and (b), the interference light signal removal efficiency can be further improved.
(C) More than twice the optical frequency bandwidth of the interfering light signal.

Here, the condition (a) will be described with a specific example. FIG. 3 is a schematic diagram showing the light intensity when the interference light signal 70g is removed by the optical communication system 100 of the present embodiment. In FIG. 3, the thin dotted line indicates the optical frequency characteristics of the Mach-Zehnder interferometer 91 shown in FIG. 2 as the interfering light signal remover 21 shown in FIG. 1, and the thin solid line applies the Mach-Zehnder interferometer as the optical decoder 14. The frequency characteristics are shown. Here, the half-cycle of the Mach-Zehnder interferometer as the optical decoder 14 is set as the chip width of the code, and is encoded with the code in the optical frequency region of 101010. A thin dotted line indicates the optical frequency characteristics of the communication optical signal 70c transmitted by the optical transmitter 10 shown in FIG. 1, and a thick solid line indicates that the communication optical signal 70d on which the interference optical signal 70g is superimposed is the interference optical signal. The optical frequency characteristics after passing through the Mach-Zehnder interferometer 91 shown in FIG. 2 as the remover 21 and the Mach-Zehnder interferometer as the optical decoder 22 are shown. Here, the period of the optical frequency characteristic of the Mach-Zehnder interferometer 91 shown in FIG. 2 as the interfering light signal remover 21 is set to the code of the Mach-Zehnder interferometer as the optical encoder 22 so as to satisfy the condition (A). It was set to 1/2 of the optical frequency width of the chip constituting the chip. FIG. 3A shows that when the optical frequency of the interfering optical signal 70g is Fd ₁ , the optical path length difference in the Mach-Zehnder interferometer 91 as the interfering optical signal remover 21 is adjusted to adjust the interfering optical signal 70g. FIG. 3B shows the optical intensity when matched with the frequency, and FIG. 3B shows the optical frequency of the interfering optical signal 70 g without changing the optical frequency width of the Mach-Zehnder interferometer 91 as the interfering optical signal remover 21. Shows the light intensity when f is changed from fd ₁ to fd ₂ .

As shown by the thick solid line in FIG. 3A, it can be seen that even when the interfering light signal 70g having the optical frequency fd ₁ is removed, the light intensity exceeds 50% and sufficient light intensity can be secured. Further, as shown by the thick solid line in FIG. 3B, even when the optical frequency is changed from fd ₁ to fd ₂ , the light intensity after passing substantially matches the light intensity of the communication optical signal 70c. It can be seen that sufficient light intensity can be secured.

  In the present embodiment, a Mach-Zehnder interferometer is applied as the interfering light signal remover 21 shown in FIG. 1. However, other interferometers using an optical path length difference, such as a Michelson interferometer, a Fabry, are used. It can be realized by a Perot interferometer, AWG or the like. In the case of a Mach-Zehnder interferometer, Michelson interferometer, and Fabry-Perot interferometer, the optical path length difference can be converted by Equation 3, and in the case of an AWG (arrayed waveguide grating), converted by Equation 4 below. It shall be. Further, for example, a plurality of optical couplers may be connected in cascade to combine the branched optical signals from the respective optical couplers.

  As described above, in the optical communication system 100 according to the present embodiment, the interference optical signal 70g between the optical transmission device 10 and the optical reception device 20 has a narrow optical frequency band or a long coherence length and a high light intensity. Even if the interference light signal 70g having a wide pulse interval and a high light intensity is combined, the interference light signal 70g can be removed by the optical receiver 20, so that highly accurate optical communication can be realized. In the optical communication system 100 according to the present embodiment, the optical receiver 20 has the characteristics. In the optical receiver 20 according to the present embodiment, the optical frequency band is narrow or the coherence length is long. Even if the interference light signal 70g having a high intensity or the communication light signal 70d having a wide pulse interval and a high light intensity combined is received, the interference light signal 70g can be removed, thereby realizing high-precision optical reception. can do.

  Here, an optical communication method in the optical communication system 100 according to the present embodiment will be described with reference to FIG.

  In the optical communication method in the optical communication system 100 according to the present embodiment, the communication optical signal 70c spread-coded in the optical frequency domain is transmitted between the optical transmitter 10 and the optical receiver 20 via the optical transmission path 67. Send and receive.

  That is, the optical modulator 12 modulates, for example, the intensity of the optical signal 70a output from the light source 11 of the optical transmitter 10 based on the communication signal 60a, and outputs the modulated optical signal 70b to the optical encoder 14. For example, the optical encoder 14 divides the optical frequency band of the modulated optical signal 70b into a plurality of signals based on the optical diffusion code, and outputs the communication optical signal 70c that is spread-encoded to the optical receiving device 20.

  The communication optical signal 70c transmitted from the optical transmitter 10 includes an interference optical signal 70g having a relatively narrow frequency bandwidth and an interference light having a long coherence length between the optical transmitter 10 and the optical receiver 20. The signal 70g may be coupled through the optical multiplexer 65. Therefore, in this case, the optical receiving device 20 receives the communication optical signal 70d on which the interference light signal 70g is superimposed.

  The optical receiver 20 removes the interfering optical signal 70g by branching the communication optical signal 70d transmitted from the optical transmitter 10 into two or more by the interfering optical signal remover 21 and combining them with a predetermined optical path length difference. Output. The communication optical signal 70e output from the interfering optical signal remover 21 is decoded by the optical decoder 22 corresponding to the optical encoder 14 to restore the frequency characteristic of the modulated optical signal 70b, and then directed to the photodetector 23. Is output. The photodetector 23 detects the communication signal 60a of the optical transmission device 10 by converting the communication optical signal 70f decoded by the optical decoder into an electric signal 60b.

  Here, the predetermined optical path length difference is equal to or greater than a value obtained by converting the optical frequency bandwidth of the communication optical signal 70c transmitted from the optical transmitter 10 into a length or greater than the coherence length of the communication optical signal 70c. Alternatively, when the communication optical signal 70c is a pulse optical signal, the pulse width of the communication pulse optical signal as the communication optical signal 70c is set to a value converted to a length or more. By setting the optical path length difference to one of the above lengths, the interference light signal 70g can be efficiently removed while ensuring the light intensity of the communication optical signal 70e after passing through the interference light signal remover 21. it can.

As described above, in the optical communication method according to the present embodiment, the interfering optical signal 70g having a narrow optical frequency band or a long coherence length and a high light intensity between the optical transmitting apparatus 10 and the optical receiving apparatus 20 Even if the interfering light signal 70g having a wide pulse interval and a large light intensity is combined, the interfering light signal 70g can be removed by the optical receiving device 20, so that highly accurate optical communication can be realized.
(Second Embodiment)

  FIG. 4 shows a schematic configuration diagram of an optical multiplex communication system according to the present embodiment. An optical multiplex communication system 101 shown in FIG. 4 includes a first optical transmission device 10 that transmits a communication optical signal 70c that is spread-coded in the optical frequency domain, and a communication optical signal 70j that is different from the communication optical signal 70c. An optical multiplexer 65 that connects the second optical transmission device 30 to transmit, the first and second optical transmission devices 10 and 30, and an optical signal for communication 70c transmitted from the first optical transmission device 10 are optically multiplexed. A first optical receiver 20 that receives the optical signal for communication 70j transmitted from the second optical transmitter 30 via the optical multiplexer 65; And an optical demultiplexer 66 for connecting the second optical receivers 20 and 40.

  In the present embodiment, the first optical transmission device described in the first embodiment is added to the existing optical communication system that does not use the optical CDM method, which is configured by the existing second optical transmission device 30 and the second optical reception device 40. 10 shows an embodiment in which an optical CDM optical communication system composed of 10 and the first optical receiver 20 is added. Here, the same components as those described in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  The second optical transmission device 30 includes a light source 32 and an optical modulator 33, and the second optical reception device includes a detector 41 corresponding to the optical modulator 33. The optical modulator 33 is an optical modulator that performs optical frequency modulation, optical intensity modulation, optical phase modulation, or the like based on the communication signal 60c.

  An optical directional coupler, an optical coupler, a WDM (Wavelength Division Multiplex) coupler, or the like can be applied to the optical multiplexer 65 and the optical demultiplexer 66. In this embodiment, the optical multiplexer 65 and the optical demultiplexer 66 are provided separately. However, the first and second optical multiplexers having both functions of the optical multiplexer 65 and the optical demultiplexer 66 are used. Two optical transceivers 10, 20, 30, and 40 may be combined.

  In the existing optical communication system, in order to improve the communication accuracy without using the optical CDM system, the communication optical signal 70j having a small optical frequency bandwidth and a high light intensity is used. Therefore, when the optical CDM optical communication system described in the first embodiment is added to the existing communication system, the communication optical signal 70j transmitted from the second optical transmission device 30 passes through the optical multiplexer 65. This is combined with the communication optical signal 70c transmitted from the first optical transmission device 10. Then, the communication optical signal 70d combined with the communication optical signal 70j transmitted from the second optical transmission device 30 passes through the optical demultiplexer 66 and is received by the first optical reception device 20 as it is. . Here, when the optical frequency of the communication optical signal 70 c transmitted from the first optical transmission device 10 and the optical frequency of the communication optical signal 70 j transmitted from the second optical transmission device 30 are different, the optical demultiplexer 66. Depending on the wavelength dependency, the communication optical signal 70c transmitted from the first optical transmission device 10 and the communication optical signal 70j transmitted from the second optical transmission device 30 may be demultiplexed. However, when the optical frequency of the communication optical signal 70a transmitted from the first optical transmitter 10 matches the optical frequency of the communication optical signal 70j transmitted from the second optical transmitter 30, the optical demultiplexer 66 is used. Therefore, the communication optical signal 70a transmitted from the first optical transmitter 10 and the communication optical signal 70j transmitted from the second optical transmitter 30 cannot be demultiplexed.

  Therefore, the optical signal for communication 70j transmitted from the second optical transmitter 30 and being an interfering optical signal for the first optical receiver 20 is removed by the interfering optical signal remover 21 of the first optical receiver 20. The configuration of the interference light signal remover 21 of the first optical receiver 20 is substantially the same as that described in the first embodiment. However, in this embodiment, the setting of the optical path length difference of the interfering light signal remover 21 is further set to the following value in addition to the configuration described in the first embodiment. That is, in the present embodiment, the optical path length difference is equal to or larger than the value obtained by converting the optical frequency bandwidth of the communication optical signal 70c into the length, and the optical frequency bandwidth of the communication optical signal 70j transmitted by the second optical transmission device 30 is set. The value converted into the length or less, or the coherence length of the communication optical signal 70c transmitted by the first optical transmission device 10 and the coherence length of the communication optical signal 70j transmitted by the second optical transmission device 30. . Here, the “value obtained by converting the optical frequency bandwidth of the communication optical signal 70c into a length” is converted according to Equation 3 or 4, and “the optical frequency bandwidth of the communication optical signal 70j is converted into a length. When the interfering light signal remover 21 is a Mach-Zehnder interferometer, a Michelson interferometer, or a Fabry-Perot interferometer, the optical path length difference is converted by Equation 5 and the converted value is calculated by AWG (arrayed waveguide diffraction grating). In this case, conversion is performed according to the following Equation 6.

  When the communication optical signals 70c and 70j transmitted by the first and second optical transmission devices 10 and 30 are pulse optical signals, the optical path length difference is set as the communication optical signal 70c transmitted by the first optical transmission device 10. More than or equal to the value obtained by converting the pulse width of the communication pulse optical signal to the length and not more than the value obtained by converting the pulse width of the communication pulse optical signal as the communication optical signal 70j transmitted by the second optical transmitter 30 to the length. And The communication optical signal 70j transmitted by the second optical transmitter 30 may be either an RZ (Return-To-Zero) signal or an NRZ (Non-Return-To-Zero) signal.

  As described in the first embodiment, the interference optical signal remover 21 of the first optical receiver 20 can remove the communication optical signal 70j transmitted from the second optical transmitter 30. The optical frequency bandwidth of the communication optical signal 70j transmitted from the optical transmission device 30 is smaller than the optical frequency bandwidth of the communication optical signal 70c transmitted from the first optical transmission device 10, or from the second optical transmission device 30. This is because the coherence length of the transmitted communication optical signal 70j is longer than the coherence length of the communication optical signal 70c transmitted from the first optical transmission device 10. Further, in the optical CDM system, when the communication optical signal 70c transmitted from the first optical transmission device 10 is a communication pulse optical signal, the communication optical signal 70c is encoded by a spread code. This is because the pulse width of the communication optical signal 70 c is smaller than the pulse width of the communication pulse optical signal transmitted from the second optical transmitter 30.

  As described above, in the optical multiplex communication system 101 according to the present embodiment, the communication optical signal 70j used in the existing optical communication system that does not use the optical CDM system and the optical CDM system described in the first embodiment. In addition to the case where the optical frequency of the optical signal for communication 70c used in the optical communication system is different, even if the optical frequency is the same, it is possible to realize highly accurate single-frequency optical multiplex communication without causing mutual interference. it can. The optical multiplex communication system 101 according to the present embodiment has the characteristics of the optical receiver 20. The optical receiver 20 according to the present embodiment has a communication optical signal 70 in the existing optical communication system. Even when the communication optical signal 70j having the same frequency as that of the communication optical signal 70j is received together with the communication optical signal 70c of the existing optical communication system, the communication optical signal 70j can be removed. Accurate optical reception can be realized.

  Here, an optical multiplex communication method in the optical multiplex communication system 101 according to the present embodiment will be described with reference to FIG.

  In the optical multiplex communication method in the optical multiplex communication system 101 according to the present embodiment, a communication optical signal 70c spread-coded in the optical frequency domain is transmitted between the first optical transmission device 10 and the first optical reception device 20. A communication optical signal 70j different from the communication optical signal 70c is transmitted / received between the second optical transmitter 30 and the second optical receiver 40 via the optical transmission path 67.

  That is, the optical signal 70 a output from the light source 11 of the first optical transmission device 10 is, for example, intensity-modulated based on the communication signal 60 a by the optical modulator 12, and the modulated optical signal 70 b is output toward the optical encoder 14. . For example, the optical encoder 14 divides the optical frequency band of the modulated optical signal 70b into a plurality of signals based on the optical diffusion code, performs spread encoding, and outputs the optical signal to the first optical receiver 20 as a communication optical signal 70c.

  On the other hand, the optical signal 70h output from the light source 32 of the second optical transmission device 30 is intensity-modulated by the optical modulator 33 based on the communication signal 60c, for example, and is transmitted to the second optical reception device 40 as a communication optical signal 70j. Output.

  The communication optical signal 70 j transmitted from the second optical transmission device 30 is coupled to the communication optical signal 70 c transmitted from the first optical transmission device 10 via the optical multiplexer 65. Therefore, the first optical receiving device receives the communication optical signal 70d on which the communication optical signal 70j that is an interfering optical signal is superimposed.

  The first optical receiving device 20 divides the communication optical signal 70d received by the first optical receiving device 20 into two or more by the interfering optical signal remover 21 and combines them by providing a predetermined optical path length difference, thereby interfering optical signals. The communication optical signal 70j is removed and output. The optical signal for communication 70e output from the interfering optical signal remover 21 is decoded by the optical decoder 22 corresponding to the optical encoder 14 to restore the optical frequency characteristic of the modulated optical signal 70b, and then to the optical detector 23. Is output. The photodetector 23 detects the communication signal 60a of the first optical transmission device 10 by converting the communication optical signal 70f decoded by the optical decoder 22 into an electric signal 60b.

  Here, the predetermined optical path length difference is equal to or greater than a value obtained by converting the optical frequency bandwidth of the communication optical signal 70c into a length, and the optical frequency bandwidth of the communication optical signal 70j transmitted by the second optical transmission device 30. The value converted into the length or less, or the coherence length of the communication optical signal 70c transmitted by the first optical transmission device 10 and the coherence length of the communication optical signal 70j transmitted by the second optical transmission device 30. .

  In addition, when the communication optical signals 70c and 70j transmitted by the first and second optical transmitters 10 and 30 are pulse optical signals, the communication pulse as the communication optical signal 70c transmitted by the first optical transmitter 10 is used. The pulse width of the optical signal is equal to or greater than the value converted to the length, and the pulse width of the communication pulse optical signal as the communication optical signal 70j transmitted by the second optical transmitter 30 is equal to or less than the value converted to the length. By setting the optical path length difference to one of the above lengths, the communication optical signal 70j, which is the interference optical signal, is efficiently obtained while ensuring the optical intensity of the communication optical signal 70e after passing through the interference optical signal remover 21. Can be removed.

  On the other hand, the second optical receiver 40 receives the communication optical signal 70j transmitted from the second optical transmitter 30 together with the communication optical signal 70c transmitted from the first optical transmitter 10. However, since the optical intensity of the communication optical signal 70c transmitted from the first optical transmitter 10 is very small compared to the communication optical signal 70j transmitted from the second optical transmitter 30, the second optical receiver The reception of the 40 communication optical signals 70j is not affected. Therefore, the second optical receiver 40 detects the communication signal 60c of the second optical transmitter 30 by converting the communication optical signal 70k received by the second optical receiver 40 into an electric signal 60d by the photodetector 41. be able to.

As described above, in the optical multiplex communication system according to the present embodiment, the communication optical signal 70j used in the existing optical communication system that does not use the optical CDM system and the optical CDM system light described in the first embodiment. Of course, when the optical frequency of the optical signal for communication 70c used in the communication system is different, even when the optical frequency is the same, it is possible to realize highly accurate same-frequency optical multiplex communication without causing mutual interference. . Further, the optical multiplex communication system 101 according to the present embodiment has the characteristics of the first optical receiving device 20, and the first optical receiving device 20 according to the present embodiment has a communication function in an existing optical communication system. Even when the communication optical signal 70j having the same frequency as that of the communication optical signal 70c is used, the communication optical signal 70j is removed when the communication optical signal 70j of the existing optical communication system is received together with the communication optical signal 70c. Therefore, highly accurate optical reception can be realized.
(Third embodiment)

  FIG. 5 shows a schematic configuration diagram of an optical multiplex communication system according to the present embodiment. The optical multiplex communication system 102 shown in FIG. 5 includes a first optical transmission device 10 that transmits a communication optical signal 70c that is spread-coded in the optical frequency domain, and a communication optical signal 70j that is different from the communication optical signal 70c. An optical multiplexer 65 that connects the second optical transmission device 30 to transmit, the first and second optical transmission devices 10 and 30, and an optical signal for communication 70c transmitted from the first optical transmission device 10 are optically multiplexed. The first optical receiver 20 that receives the signal via the optical device 65, and the optical signal for communication 70j that is connected to the first optical receiver 20 and transmitted from the second optical transmitter 30. The optical multiplexer 65 and the first optical receiver And a second optical receiving device 40 that receives the signal via the second optical receiving device 20.

  In this embodiment, the configuration is substantially the same as that of the optical multiplex communication system 101 described in the second embodiment, but the second optical receiver 40 is connected to the interfering optical signal remover 21 of the first optical receiver 20. This is different from the optical multiplex communication system 101 described in the second embodiment. The second optical receiver 20 receives the communication optical signal 70j transmitted from the second optical transmitter 30 via the optical multiplexer 65 and the interfering optical signal remover 21 of the first optical receiver 20. Is different from the optical multiplex communication system 102 described in the second embodiment. Here, the same components as those described in the second embodiment have the same numbers, and the description thereof is omitted.

  The interfering optical signal remover 21 of the first optical receiving device 20 provides a predetermined optical path length difference to the branched optical signal obtained by branching the communication optical signal 70d received by the first optical receiving device 20 into two or more optical signals, The branched optical signals provided with a predetermined optical path length difference are combined and branched, one of them is output as a communication optical signal 70e inside the first optical receiver 20 with a predetermined light intensity, and the other is transmitted as communication light. The signal 70k is output toward the second optical receiver 20 outside the first optical receiver 20. With such a configuration, an optical demultiplexer that branches the communication optical signal 70d toward the second optical receiving device 20 is not provided, so that optical loss due to the optical demultiplexer can be reduced. . It is also economical.

  Here, a specific configuration example of the interfering light signal remover 21 will be described. FIG. 6 shows an example in which a Mach-Zehnder interferometer is applied as the interfering light signal remover 21. The Mach-Zehnder interferometer shown in FIG. 6 is substantially the same as that described in FIG. 2, and therefore, the same components as those shown in FIG.

  In the Mach-Zehnder interferometer 92 as the interference light signal remover 21 shown in FIG. 6, the branched light signal 80d of the branched light signal 80b transmitted through the half mirror 53 and the branched light reflected by the half mirror 53 of the branched light signal 80a. The signal 80c is condensed on the optical fiber 58 by the lens 59, and the communication optical signal 70k is transmitted to the second optical receiver 40 shown in FIG.

  The branched optical signals 80a and 80b include a communication optical signal 70j transmitted from the second optical transmission device 30 shown in FIG. By adjusting the optical path length difference between the branched optical signals 80a and 80b and outputting the optical signal for communication 70j to the optical signal for communication 70k, the second optical receiver 40 can generate a signal based on the optical signals 80c and 80d. The communication signal 60c of the second optical transmission device 30 shown in FIG. 5 can be detected.

  In the present embodiment, the Mach-Zehnder interferometer 92 is used as the interfering light signal remover 21. However, other interferometers using an optical path length difference, such as a Michelson interferometer and a Fabry-Perot interferometer, are described. , AWG or the like. Further, for example, a plurality of optical couplers may be connected in cascade to combine the branched optical signals from the respective optical couplers.

  As described above, in the optical multiplex communication system 102 according to the present embodiment, the communication optical signal 70j used in the existing optical communication system that does not use the optical CDM system and the optical CDM system described in the first embodiment. In addition to the case where the optical frequency of the optical signal for communication 70c used in the optical communication system is different, even if the optical frequency is the same, it is possible to realize highly accurate single-frequency optical multiplex communication without causing mutual interference. it can. Furthermore, since there is no optical demultiplexer that branches the communication optical signal 70d toward the second optical receiving device, it is possible to reduce optical loss due to the optical demultiplexer. It is also economical. Further, the optical multiplex communication system 102 according to the present embodiment has the characteristics of the first optical receiving device 20, and the first optical receiving device 20 according to the present embodiment has a communication function in an existing optical communication system. Even when the communication optical signal 70j having the same frequency as that of the communication optical signal 70c is used, the communication optical signal 70j is removed when the communication optical signal 70j of the existing optical communication system is received together with the communication optical signal 70c. Therefore, highly accurate optical reception can be realized. Furthermore, since there is no optical demultiplexer that branches the communication optical signal 70d toward the second optical receiver 40, optical loss due to the optical demultiplexer can be reduced. It is also economical.

  Here, the optical multiplex communication method in the optical multiplex communication system 102 according to the present embodiment will be described with reference to FIG. 5 for differences from the optical multiplex communication method described in the second embodiment.

  In the optical multiplex communication method in the optical multiplex communication system 102 according to the present embodiment, a communication optical signal 70c spread-coded in the optical frequency domain is transmitted between the first optical transmission device 10 and the first optical reception device 20. Transmission / reception is performed via the transmission path 67, and a communication optical signal 70 j different from the communication optical signal 70 c is transmitted / received between the second optical transmission apparatus 30 and the second optical reception apparatus 40 via the optical transmission path 67.

  That is, the first optical receiver 20 branches the communication optical signal 70d received by the first optical receiver 20 into two or more by the interference optical signal remover 21, and gives a predetermined optical path length difference to the branched optical signal. The branched optical signal having the optical path length difference is combined and branched, and the communication optical signal 70j that is the interference optical signal is removed from one of the branched optical signals and output. At the same time, the interfering light signal remover 21 outputs the other toward the second optical receiver 40.

As described above, in the optical multiplex communication system 102 according to the present embodiment, the communication optical signal 70j used in the existing optical communication system that does not use the optical CDM system and the optical CDM system described in the first embodiment. In addition to the case where the optical frequency of the optical signal for communication 70c used in the optical communication system is different, even if the optical frequency is the same, it is possible to realize highly accurate single-frequency optical multiplex communication without causing mutual interference. it can. Furthermore, since an optical demultiplexer that branches the communication optical signal 70d to the second optical receiver 40 is not provided, optical loss due to the optical demultiplexer can be reduced. It is also economical.
(Fourth embodiment)

  FIG. 7 shows a schematic configuration diagram of an optical multiplex communication system according to the present embodiment. In the present embodiment, in the optical multiplex communication system 101 (FIG. 4) shown in the second embodiment, the light source 11 of the first optical transmitter 10, the optical encoder 14, and the interference optical signal removal of the first optical receiver 20 are removed. Specific devices were applied to the detector 21, the optical decoder 22, and the photodetector 23. Note that the same components as those described in the second embodiment are denoted by the same reference numerals and description thereof is omitted.

  In this embodiment, the light source 15 includes an SLD that outputs light having a short coherence length, an optical amplifier, and an optical filter having a center frequency of 1555 nm and a half-value width of 8 nm.

  Further, a light intensity modulator is applied as the light modulator 16. Based on the communication signal 60a, the optical signal 70a output from the light source 15 is output as complementary modulated optical signals 90a and 90b whose light intensity is inverted.

  The Mach-Zehnder type optical waveguide filter 19 as an optical encoder multiplexes / demultiplexes the two modulated optical signals 90a and 90b output from the optical modulator 16 by the optical directional coupler 17a. Then, an optical path length difference is given to one branched optical signal 90d of the Mach-Zehnder type optical waveguide 18 (FSR 10 GHz), and then combined with the other branched optical signal 90c. The branched optical signals 90c and 90d are multiplexed / demultiplexed by the optical directional coupler 17b and spread coded, and output from one output as a communication optical signal 70c having a bipolar optical frequency characteristic. The Mach-Zehnder type optical waveguide filter 29 as an optical decoder has the same configuration as the Mach-Zehnder type optical waveguide filter 19 as an optical encoder.

  A Mach-Zehnder type optical waveguide 25 (FSR 1000 GHz) (FSR: frequency bandwidth) and a Mach-Zehnder type optical waveguide filter 26 in which optical directional couplers 24a and 24b are connected to its input and output are applied as interference light signal removers. . The Mach-Zehnder type optical waveguide filter 26 serving as an interfering optical signal remover is configured such that a communication optical signal 70d on which a communication optical signal 70j transmitted from the second optical transmission device 30 is superimposed is, for example, optical intensity by an optical directional coupler 24a. And branching into two in accordance with the optical path length difference of one of the branched optical signals 90f and combining with the other branched optical signal 90e in the optical directional coupler 24b. Here, the optical directional coupler 24b can give an arbitrary coupling ratio to the branched optical signals 90e and 90f according to, for example, the light intensity. Therefore, it is possible to obtain the communication optical signal 90g from which the communication optical signal 70j, which is an interference optical signal, is removed from one output 37 of the optical directional coupler 24b. By applying the Mach-Zehnder type optical waveguide filter 26 as the interference light signal remover, the interference light signal remover can be made compact.

  Further, a differential photodetector 36 is applied as the photodetector. The differential detector 36 as a photodetector detects the light intensity of the bipolar communication optical signals 90k and 90m output from the Mach-Zehnder type optical waveguide filter 29 as an optical decoder by the light receiving elements 35 and 36. The communication signal 60a of the first optical transmission device 10 is detected by converting and taking the difference.

  Here, a specific removal effect of the interfering optical signal in the optical receiver 20 in the optical multiplex communication system 103 according to this example will be described. FIG. 8 shows communication after passing through a Mach-Zehnder type optical waveguide filter 29 as an optical decoder when the interference light signal is removed by the Mach-Zehnder type optical waveguide filter 26 as an interference light signal remover. The optical frequency spectrum of the optical signal for use 70d is shown. FIG. 8A shows an optical frequency spectrum when the interference light signal is removed by the Mach-Zehnder optical waveguide filter 26 as the interference light signal remover, and FIG. 8B shows the interference light signal remover. The optical frequency spectrum when the interference light signal is not removed by the Mach-Zehnder type optical waveguide filter 26 is shown. In order to verify the removal effect of the Mach-Zehnder type optical waveguide filter 26 as an interfering light signal remover, the optical modulator 16 intensifies the optical signal 70a according to a 1 Gbit / s, 31-stage pseudo-random signal from the pulse pattern generator. It was decided to modulate. Further, as the interfering light signal, an optical signal having a center frequency of 1555 nm and a half-value width of 130 MHz modulated with a 1 Gbit / s, 31-stage pseudo-random signal was used. The spectrum in FIG. 8 is a spectrum in which the interference effect is verified by inputting the interference light signal from the input 39 different from the input of the communication optical signal 70d of the Mach-Zehnder optical waveguide filter 26 as the interference light signal remover. . For this reason, the spectrum in an actual structure becomes a form different from the spectrum of FIG.

  As shown in FIG. 8B, in the case where the Mach-Zehnder type optical waveguide filter 26 as the interference light signal remover is not provided, the influence of the interference light signal is large and the optical frequency has a peak at 1555 nm. Recognize. On the other hand, in the case where the Mach-Zehnder type optical waveguide filter 26 as the interference light signal remover is provided, the interference light signal having an optical frequency of 1555 nm is suppressed by 20 dB or more as shown in FIG. It can be seen that the interference light signal can be removed by the Mach-Zehnder type optical waveguide filter 26 as the signal remover.

  Further, FIG. 9 shows a Mach-Zehnder type as an optical decoder when the interference light signal is removed by the Mach-Zehnder type optical waveguide filter 26 as the interference light signal remover, and when the interference light signal is not removed and when there is no interference light signal. The eye pattern of the optical signal for communication 70d after passing through the optical waveguide filter 29 is shown. FIG. 9A shows an eye pattern of the communication optical signal 70c when there is no interfering optical signal, and FIG. 9B shows that the interfering optical signal is removed by the Mach-Zehnder optical waveguide filter 26 as an interfering optical signal remover. FIG. 9C shows an eye pattern of the communication optical signal 70c after passing through the Mach-Zehnder type optical waveguide filter 29 as an optical decoder. FIG. The eye patterns of the communication optical signal 70c after passing through the Mach-Zehnder type optical waveguide filter 29 as an optical decoder when the optical signal is not removed are shown. In FIG. 9, the horizontal axis represents time, and the vertical axis represents light intensity. One scale on the vertical axis is 20 nW / div in FIGS. 9A and 9B and 40 nW / div in FIG. 9C, respectively. In this example, the intensity ratio between the interference light signal and the communication optical signal is 16 dB, which is sufficiently smaller than the extinction ratio of the interference light signal. Since the eye pattern shown in FIG. 9B substantially matches the eye pattern shown in FIG. 9A, the interference light signal is removed by the Mach-Zehnder optical waveguide filter 29 as the interference light signal remover. You can see that

  Here, the optical multiplex communication method in the optical multiplex communication system 103 according to the present embodiment will be described with reference to FIG. 7 for differences from the optical multiplex communication method described in the second embodiment. That is, since the communication between the second optical transmitter 30 and the second optical receiver 40 is the same as that described in the second embodiment, the description thereof is omitted.

  First, the optical signal 70a output from the light source 15 is intensity-modulated by the optical modulator 16 based on the communication signal 60a, and complementary modulated optical signals 90a and 90b whose optical intensities are inverted from each other are Mach-Zehnders as optical encoders. Output toward the optical waveguide filter 19. The Mach-Zehnder type optical waveguide filter 19 serving as an optical encoder divides the optical frequency band of the modulated optical signals 90a and 90b into a plurality of signals based on the optical frequency characteristics of the filter and performs spread encoding to obtain a communication optical signal 70c. Output to one optical receiver 20. Here, since the complementary modulated optical signals 90a and 90b output from the optical modulator 16 are subjected to spread encoding, the optical frequency characteristic is bipolar from the output of the Mach-Zehnder type optical waveguide filter 19 as an optical encoder. Communication optical signal 70c is output.

  The first optical receiver 10 removes and outputs the communication optical signal 70j, which is an interference optical signal superimposed on the communication optical signal 70c, by the Mach-Zehnder optical waveguide filter 26 as an interference optical signal remover. Here, the Mach-Zehnder type optical waveguide filter 26 as an interference light signal remover uses the optical directional coupler 24a to transmit the communication optical signal 70d on which the communication optical signal 70j transmitted from the second optical transmission device 30 is superimposed. Branches to branched optical signals 90e and 90f. Thereafter, an optical path length difference is given to one of the branched optical signals 90f, and the optical signals are coupled by the optical directional coupler 24b. The optical directional coupler 24 b branches the combined branched optical signals 90 e and 90 f and outputs a communication optical signal 90 g from which the communication optical signal 70 j that is an interference optical signal is removed from one output 37.

The communication optical signal 90g output from the optical directional coupler 24b is decoded by a Mach-Zehnder optical waveguide filter 29 as an optical decoder corresponding to the optical encoder, and has a bipolar optical frequency characteristic. 90k and 90m are output toward the differential detector 36 as a photodetector. The differential detector 36 as the optical detector converts the bipolar communication optical signals 90k and 90m output from the Mach-Zehnder optical waveguide filter 29 as the optical decoder into electrical signals, and detects the difference value. To do.
(Fifth embodiment)

  FIG. 10 shows a schematic configuration diagram of an optical multiplex communication system according to the present embodiment. In the present embodiment, in the optical multiplex communication system 102 (FIG. 5) shown in the third embodiment, the light source 11 of the first optical transmitter 10, the optical encoder 14, and the interference optical signal removal of the first optical receiver 20 are removed. Specific devices were applied to the detector 21, the optical decoder 22, and the photodetector 23. Specifically, the output 38 of the Mach-Zehnder optical waveguide filter 26 described in the fourth embodiment is connected to the second optical receiver 40. The same components as those described in the second and fourth embodiments are denoted by the same reference numerals and the description thereof is omitted.

  The optical directional coupler 24b of the Mach-Zehnder type optical waveguide filter 26 can branch the branched optical signals 90e and 90f from the Mach-Zehnder type optical waveguide 25 with an arbitrary light intensity. Therefore, it becomes possible to output the communication optical signal 70j, which is an interfering optical signal, from one output 38 of the optical directional coupler 24b. In this case, from one output 38 of the optical directional coupler 24b, the communication optical signal 70c transmitted from the first optical transmitter 10 is output together with the communication optical signal 70j. However, since the optical intensity of the communication optical signal 70c transmitted from the first optical transmitter 10 is very small compared to the optical intensity of the communication optical signal 70j transmitted from the second optical transmitter, the second light The reception of the communication optical signal 70j by the receiving device 40 is not affected. Therefore, the second optical receiving device 40 converts the communication optical signal 70k transmitted via the first optical receiving device 20 into an electric signal 60d by the photodetector 41, and transmits the communication signal 60c of the second optical transmitting device 30. Can be detected. Further, the interference light signal remover can be made compact by applying the Mach-Zehnder type optical waveguide filter 26 as the interference light signal remover. Furthermore, since an optical demultiplexer for branching the communication optical signal 70d to the second optical receiver 40 is not provided, optical loss due to the optical demultiplexer can be reduced. It is also economical.

  Here, the optical multiplex communication method in the optical multiplex communication system 104 according to the present embodiment will be described with reference to FIG. 10 for differences from the optical multiplex communication method described in the fourth embodiment. Note that the operation of each device except the Mach-Zehnder type optical waveguide filter 26 as an interference light signal remover is the same as that described in the second and fourth embodiments, and a description thereof will be omitted.

  The Mach-Zehnder type optical waveguide filter 26 serving as an interfering optical signal remover of the first optical receiving device 20 converts an optical signal on which a communication optical signal 70j transmitted from the second optical transmitting device 30 is superimposed into an optical directional coupler 24a. Branches to branched optical signals 90e and 90f. Thereafter, an optical path length difference is given to one of the branched optical signals 90f, and the optical signals are coupled by the optical directional coupler 24b. Here, in the optical directional coupler 24b, the combined branched optical signals 90e and 90f are branched, and from one output 37, the communication optical signal 90g from which the communication optical signal 70j which is an interference optical signal is removed is obtained. The other output 38 outputs the communication optical signal 70k including the communication optical signal 70j transmitted from the second optical transmitter 30.

  The second optical receiver 40 receives the communication optical signal 70k output from the other output 38 of the optical directional coupler 24b. The optical signal for communication 70c in the optical CDM system does not affect the reception of the optical signal for communication 70j of the second optical receiver 40 because the light intensity is weak.

  In the optical communication system, the optical multiplex communication system, the optical communication method, the optical multiplex communication method, and the optical receiving apparatus of the present invention, it can be widely used from a long distance trunk line to an access line.

1 is a schematic configuration diagram of an optical communication system according to a first embodiment. It is a schematic block diagram of the Mach-Zehnder interferometer as an interference light signal remover. It is the schematic which showed the light intensity in the case of removing an interference light signal with an interference light signal remover. It is a schematic block diagram of the optical multiplex communication system which concerns on 2nd Embodiment. It is a schematic block diagram of the optical multiplex communication system which concerns on 3rd Embodiment. It is the figure which showed the example which applied the Mach-Zehnder interferometer as an interference light signal remover of the optical multiplex communication system which concerns on 3rd Embodiment. It is a schematic block diagram of the optical multiplex communication system which concerns on 4th Embodiment. It is the figure which showed the optical frequency spectrum of the optical signal for communication after the optical decoder in the case where an interference optical signal is removed, and the case where it is not removed. It is the figure which showed the eye pattern of the optical signal for communication after the optical decoder in the case where an interference light signal is removed, the case where it does not remove, and the case where there is no interference light signal. It is a schematic block diagram of the optical multiplex communication system which concerns on 5th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical transmitter, 1st optical transmitter 11, 15, 32 Light source 12, 16, 33 Optical modulator 14 Optical encoder 17a, 17b, 24a, 24b, 27a, 27b Optical directional coupler 18, 25, 28 Mach Zehnder type optical waveguide 19, 26, 29 Mach-Zehnder type optical waveguide filter 20 Optical receiver, first optical receiver 21 Interfering optical signal remover 22 Optical decoder 23, 41 Photodetector 30 Second optical transmitter 35a, 35b Light receiving element 36 Differential detector 37, 38 Output 39 Input 40 Second optical receiver 50, 53, 57 Half mirror 51 Phase delay unit 52, 54 Mirror 55, 59 Lens 56, 58 Optical fiber 60a, 60c Communication signal 60b, 60d Electric signal 65 Optical multiplexer 66 Optical demultiplexer 67 Optical transmission line 70a, 70h Optical signal 70b, 90a, 90b, 90h Optical signals 70c, 70d, 70g, 70k, 70m, 70j, 70k, 90g communication optical signals 80a, 80b, 80c, 80d, 90c,
90d, 90e, 90f, 90i, 90j Branched optical signal 91, 92 Mach-Zehnder interferometer
100 Optical Communication System 101, 102, 103 Optical Multiplex Communication System

Claims (24)

An optical communication system comprising: an optical transmission device that transmits an optical signal for communication that is spread-encoded in an optical frequency domain; and an optical reception device that receives the optical signal for communication transmitted from the optical transmission device. ,
The optical receiver is
The optical signal for communication transmitted from the optical transmitter is branched into two or more, and the optical frequency bandwidth of the optical signal for communication is provided with an optical path length difference equal to or greater than the length, and combined with predetermined light. Interference light signal remover that outputs with intensity,
A photodetector for detecting the communication optical signal output from the interfering optical signal remover;
An optical communication system comprising: An optical communication system comprising: an optical transmission device that transmits an optical signal for communication that is spread-encoded in an optical frequency domain; and an optical reception device that receives the optical signal for communication transmitted from the optical transmission device. ,
The optical receiver is
An interfering optical signal remover for branching the optical signal for communication transmitted from the optical transmitter into two or more, providing an optical path length difference equal to or greater than the coherence length of the optical signal for communication, and outputting the optical signal with a predetermined intensity. When,
A photodetector for detecting the communication optical signal output from the interfering optical signal remover;
An optical communication system comprising: An optical communication system comprising: an optical transmission device that transmits a communication pulse optical signal that is spread-encoded in an optical frequency domain; and an optical reception device that receives the communication pulse optical signal transmitted from the optical transmission device. There,
The optical receiver is
The communication pulse optical signal transmitted from the optical transmission device is branched into two or more, and a predetermined light is combined by providing an optical path length difference equal to or greater than a value obtained by converting the pulse width of the communication pulse optical signal into a length. Interference light signal remover that outputs with intensity,
A photodetector for detecting the communication pulse optical signal output from the interfering optical signal remover;
An optical communication system comprising: A first optical transmission device that transmits a communication optical signal spread-encoded in an optical frequency domain; and a second optical transmission device that transmits another communication optical signal having an optical frequency bandwidth narrower than the optical frequency bandwidth of the communication optical signal. Two optical transmitters, an optical multiplexer connecting the first optical transmitter and the second optical transmitter, and the communication optical signal transmitted from the first optical transmitter via the optical multiplexer , A second optical receiver that receives the other optical signal for communication transmitted from the second optical transmitter via the optical multiplexer, and the first optical receiver And an optical demultiplexer for connecting the second optical receiver,
The first optical receiver is
The optical signal received by the first optical receiver is branched into two or more optical signals, and the optical frequency bandwidth of the optical signal for communication is equal to or greater than the length and the other optical signal for communication An interfering optical signal remover that outputs an optical frequency bandwidth with a predetermined light intensity by combining an optical path length difference equal to or less than a value obtained by converting the optical frequency bandwidth into a length; and
A photodetector for detecting the optical signal output from the interfering optical signal remover;
An optical multiplex communication system comprising: A first optical transmitter that transmits a communication optical signal spread-encoded in an optical frequency domain, and a second optical signal that transmits another communication optical signal having a coherence length longer than the coherence length of the communication optical signal. A transmission device; an optical multiplexer connecting the first optical transmission device and the second optical transmission device; and the communication optical signal transmitted from the first optical transmission device via the optical multiplexer. A first optical receiver, a second optical receiver that receives the other optical signal for communication transmitted from the second optical transmitter via the optical multiplexer, the first optical receiver, and the An optical demultiplexing system having an optical demultiplexer for connecting the second optical receiving device,
The first optical receiver is
An optical signal received by the first optical receiver is branched into two or more optical signals, and an optical path length difference equal to or greater than the coherence length of the communication optical signal and less than or equal to the coherence length of the other communication optical signal is provided. An interfering light signal remover that combines and outputs at a predetermined light intensity;
A photodetector for detecting the optical signal output from the interfering optical signal remover;
An optical multiplex communication system comprising: A first optical transmission device that transmits a communication pulse optical signal that is spread-encoded in the optical frequency domain; and a second optical transmission device that transmits another communication pulse optical signal having a pulse width larger than the pulse width of the communication pulse optical signal. An optical transmitter for connecting the first optical transmitter to the second optical transmitter; and the communication pulse optical signal transmitted from the first optical transmitter via the optical multiplexer. , A second optical receiver for receiving the other optical pulse signal for communication transmitted from the second optical transmitter through the optical multiplexer, and the first optical receiver. An optical demultiplexer for connecting a device and the second optical receiver,
The first optical receiver is
The pulse optical signal received by the first optical receiver is branched into two or more optical signals, and the pulse width of the other communication pulse optical signal is equal to or greater than the value obtained by converting the pulse width of the communication pulse optical signal into a length. An interference light signal remover that outputs an optical path with a predetermined light intensity by combining an optical path length difference equal to or less than a value converted into a length;
A photodetector for detecting the pulsed optical signal output from the interfering optical signal remover;
An optical multiplex communication system comprising: A first optical transmission device that transmits a communication optical signal spread-encoded in an optical frequency domain; and a second optical transmission device that transmits another communication optical signal having an optical frequency bandwidth narrower than the optical frequency bandwidth of the communication optical signal. Two optical transmitters, an optical multiplexer connecting the first optical transmitter and the second optical transmitter, and the communication optical signal transmitted from the first optical transmitter via the optical multiplexer And the other optical signal for communication transmitted from the second optical transmission device via the optical multiplexer and the first optical reception device, connected to the first optical reception device. An optical multiplex communication system having a second optical receiving device for receiving
The first optical receiver is
The optical signal received by the first optical receiver is branched into two or more optical signals, and the optical frequency bandwidth of the optical signal for communication is equal to or greater than the length and the other optical signal for communication An optical path length difference equal to or less than a value obtained by converting the optical frequency bandwidth into a length is provided, the branched optical signals provided with the optical path length difference are combined and branched, and one of the first light beams with a predetermined light intensity is provided. An interfering optical signal remover that outputs to the inside of the receiving device and outputs the other toward the second optical receiving device;
A photodetector for detecting the optical signal output from the interfering optical signal remover to the inside of the first optical receiver;
An optical multiplex communication system comprising: A first optical transmitter that transmits a communication optical signal spread-encoded in an optical frequency domain, and a second optical signal that transmits another communication optical signal having a coherence length longer than the coherence length of the communication optical signal. A transmission device; an optical multiplexer connecting the first optical transmission device and the second optical transmission device; and the communication optical signal transmitted from the first optical transmission device via the optical multiplexer. A first optical receiving device that receives the second optical transmission device connected to the first optical receiving device and transmitted from the second optical transmitting device via the optical multiplexer and the first optical receiving device. An optical multiplex communication system having a second optical receiver,
The first optical receiver is
An optical path length that is greater than or equal to the coherence length of the communication optical signal and less than or equal to the coherence length of the other communication optical signal to a branched optical signal obtained by branching the optical signal received by the first optical receiver into two or more optical signals Providing a difference, combining and branching the branched optical signals provided with the optical path length difference, outputting one to the inside of the first optical receiver with a predetermined light intensity, and supplying the other to the second optical receiver An interfering light signal remover that outputs to
A photodetector for detecting the optical signal output from the interfering optical signal remover to the inside of the first optical receiver;
An optical multiplex communication system comprising: A first optical transmission device that transmits a communication pulse optical signal that is spread-encoded in the optical frequency domain; and a second optical transmission device that transmits another communication pulse optical signal having a pulse width larger than the pulse width of the communication pulse optical signal. An optical transmitter for connecting the first optical transmitter to the second optical transmitter; and the communication pulse optical signal transmitted from the first optical transmitter via the optical multiplexer. A first optical receiver that receives the signal, and another communication pulse light that is connected to the first optical receiver and transmitted from the second optical transmitter via the optical multiplexer and the first optical receiver. An optical multiplex communication system having a second optical receiving device for receiving a signal,
The first optical receiver is
More than the value obtained by converting the pulse width of the communication pulse optical signal into a length to a branched optical signal obtained by branching the pulse optical signal received by the first optical receiver into two or more optical signals, and the other communication pulse light An optical path length difference equal to or less than a value obtained by converting the pulse width of the signal into a length is provided, the branched optical signals provided with the optical path length difference are combined and branched, and one of them is received with the predetermined optical intensity at the first optical reception An interfering optical signal remover that outputs to the inside of the apparatus and outputs the other to the second optical receiver;
A photodetector for detecting the pulsed optical signal output from the interfering optical signal remover to the inside of the first optical receiver;
An optical multiplex communication system comprising: An optical receiver that receives a communication optical signal that is spread-coded in the optical frequency domain,
Interference light signal elimination that outputs the optical signal with a predetermined optical intensity by branching the optical signal for communication into two or more and combining the optical signal signals for communication by providing an optical path length difference equal to or greater than the length converted into the length. And
A photodetector for detecting the communication optical signal output from the interfering optical signal remover;
An optical receiving device comprising: An optical receiver that receives a communication optical signal that is spread-coded in the optical frequency domain,
An interfering optical signal remover for branching the optical signal for communication into two or more, providing an optical path length difference equal to or greater than the coherence length of the optical signal for communication, and outputting the optical signal with a predetermined intensity;
A photodetector for detecting the communication optical signal output from the interfering optical signal remover;
An optical receiving device comprising: An optical receiver that receives a communication pulse optical signal that is spread-coded in the optical frequency domain,
Interference light signal elimination that outputs the optical signal with a predetermined light intensity by branching the communication pulse optical signal into two or more and combining them by providing an optical path length difference equal to or greater than the value obtained by converting the pulse width of the communication pulse optical signal into a length. And
A photodetector for detecting the communication pulse optical signal output from the interfering optical signal remover;
An optical receiving device comprising: An optical receiver for receiving a communication optical signal spread-coded in the optical frequency domain and another communication optical signal having an optical frequency bandwidth narrower than the optical frequency bandwidth of the communication optical signal,
The optical signal received by the optical receiver is divided into two or more optical signals, and the optical frequency bandwidth of the optical signal for communication is equal to or longer than the optical frequency bandwidth of the optical signal for communication and the light of the other optical signal for communication An optical path length difference equal to or less than a value obtained by converting a frequency bandwidth into a length is provided, and the branched optical signals provided with the optical path length difference are combined and branched, and one of them is provided with a predetermined light intensity inside the optical receiver. And an interfering optical signal remover that outputs the other to the outside of the optical receiver;
A photodetector for detecting the optical signal output from the interfering optical signal remover to the inside of the optical receiver;
An optical receiving device comprising: An optical receiver for receiving a communication optical signal spread-encoded in the optical frequency domain and another communication optical signal having a coherence length longer than the coherence length of the communication optical signal,
An optical path length difference that is greater than or equal to the coherence length of the communication optical signal and less than or equal to the coherence length of the other communication optical signal is added to a branched optical signal obtained by branching the optical signal received by the optical receiver into two or more optical signals. And branching by combining the branched optical signals provided with the optical path length difference, outputting one to the inside of the optical receiver with a predetermined light intensity, and outputting the other to the outside of the optical receiver An interfering light signal remover;
A photodetector for detecting the optical signal output from the interfering optical signal remover to the inside of the optical receiver;
An optical receiving device comprising: An optical receiver for receiving a communication pulse optical signal spread-encoded in an optical frequency region and another communication pulse optical signal having a pulse width wider than the pulse width of the communication pulse optical signal,
A branched optical signal obtained by branching a pulse optical signal received by the optical receiver into two or more optical signals is equal to or greater than a value obtained by converting the pulse width of the communication pulse optical signal into a length, and the other communication pulse optical signal An optical path length difference equal to or less than a value obtained by converting a pulse width into a length is provided, the branched optical signals provided with the optical path length difference are combined and branched, and one of the optical signals is combined to have a predetermined light intensity. An interfering optical signal remover that outputs to the outside and outputs the other to the outside of the optical receiver;
A photodetector for detecting the pulsed optical signal output from the interfering optical signal remover to the inside of the optical receiver;
An optical receiving device comprising: An optical communication method for transmitting and receiving an optical signal for communication that is spread-encoded in an optical frequency domain between an optical transmitter and an optical receiver,
The optical receiving apparatus branches the optical signal for communication transmitted from the optical transmitting apparatus into two or more, and provides an optical path length difference equal to or greater than a value obtained by converting an optical frequency bandwidth of the optical signal for communication into a length. An optical communication method comprising: detecting after combining to a predetermined light intensity. An optical communication method for transmitting and receiving an optical signal for communication that is spread-encoded in an optical frequency domain between an optical transmitter and an optical receiver,
The optical receiver splits the optical signal for communication transmitted from the optical transmitter into two or more, and provides an optical path length difference equal to or greater than the coherence length of the optical signal for communication to obtain a predetermined intensity. An optical communication method, which is detected later. An optical communication method for transmitting and receiving a communication pulse optical signal that is spread-encoded in an optical frequency domain between an optical transmitter and an optical receiver,
The optical receiving device branches the communication pulse optical signal transmitted from the optical transmission device into two or more, and provides an optical path length difference equal to or greater than a value obtained by converting a pulse width of the communication pulse optical signal into a length. An optical communication method comprising: detecting after combining to a predetermined light intensity. An optical signal for communication that is spread-encoded in the optical frequency domain is transmitted and received between the optical transmitter and the optical receiver via an optical transmission path, and an optical frequency band narrower than the optical frequency band of the optical signal for communication is separated. An optical multiplex communication method for transmitting and receiving an optical signal for communication between another optical transmitter and another optical receiver via the optical transmission path,
The optical receiver has a branch optical signal obtained by branching an optical signal received by the optical receiver into two or more optical signals, and the optical frequency bandwidth of the communication optical signal is equal to or more than a value converted into a length. An optical multiplex communication method comprising: detecting an optical frequency bandwidth of a communication optical signal after providing a predetermined optical intensity by providing an optical path length difference equal to or less than a value converted into a length. An optical signal for communication that is spread-coded in the optical frequency domain is transmitted and received between the optical transmitter and the optical receiver via an optical transmission line, and the coherence length is longer than the coherence length of the optical signal for communication. An optical multiplex communication method for transmitting and receiving an optical signal for communication between another optical transmitter and another optical receiver via the optical transmission path,
The optical receiving device branches an optical signal received by the optical receiving device into two or more optical signals, and has an optical path length that is not less than the coherence length of the communication optical signal and not more than the coherence length of the other communication optical signal. An optical multiplex communication method comprising: detecting after a difference is provided and combined to obtain a predetermined light intensity. A communication pulse optical signal spread-coded in the optical frequency domain is transmitted / received between the optical transmitter and the optical receiver via an optical transmission path, and another pulse width wider than the pulse width of the communication optical signal is transmitted. An optical multiplex communication method for transmitting and receiving a communication pulse optical signal between another optical transmission device and another optical reception device via the optical transmission path,
The optical receiving device branches the pulse optical signal received by the optical receiving device into two or more pulse optical signals, and has a value equal to or greater than a value obtained by converting the pulse width of the communication pulse optical signal into a length, and the other communication pulse. An optical multiplex communication method comprising: detecting a pulse width of an optical signal after providing a predetermined light intensity by providing an optical path length difference equal to or less than a value converted into a length. An optical signal for communication that is spread-encoded in the optical frequency domain is transmitted and received between an optical transmitter and an optical receiver via an optical transmission line, and an optical frequency bandwidth that is narrower than the optical frequency bandwidth of the optical signal for communication An optical multiplex communication method for transmitting / receiving another optical signal for communication between another optical transmitter and another optical receiver via the optical transmission path,
The optical receiver has a branch optical signal obtained by branching an optical signal received by the optical receiver into two or more optical signals, and the optical frequency bandwidth of the communication optical signal is equal to or more than a value converted into a length. An optical path length difference equal to or less than the value obtained by converting the optical frequency bandwidth of the communication optical signal into a length is provided, and the branched optical signals provided with the optical path length difference are combined and branched, and one of them is set to a predetermined light intensity. And then outputting the other to the other optical receiving apparatus. An optical signal for communication that is spread-coded in the optical frequency domain is transmitted and received between the optical transmitter and the optical receiver via an optical transmission line, and the coherence length is longer than the coherence length of the optical signal for communication. An optical multiplex communication method for transmitting and receiving an optical signal for communication between another optical transmitter and another optical receiver via the optical transmission path,
The optical receiving device branches an optical signal received by the optical receiving device into two or more optical signals, and the branched optical signal is longer than a coherence length of the communication optical signal and the other optical signal for communication. An optical path length difference equal to or shorter than the coherence length is provided, the branched optical signals provided with the optical path length difference are combined and branched, one of them is set to a predetermined light intensity, and the other is detected as another optical receiver. An optical multiplex communication method characterized by output to A communication pulse optical signal spread-coded in the optical frequency domain is transmitted / received between the optical transmission device and the optical reception device via an optical transmission path, and the pulse width of the communication pulse optical signal is larger than the pulse width of the communication pulse optical signal. An optical multiplex communication method for transmitting and receiving a communication pulse optical signal between another optical transmitter and another optical receiver via the optical transmission path,
The optical receiving apparatus branches the pulse optical signal received by the optical receiving apparatus into two or more pulse optical signals, and the branched optical signal is equal to or greater than a value obtained by converting the pulse width of the communication pulse optical signal into a length. And providing an optical path length difference equal to or less than a value obtained by converting the pulse width of the other communication optical pulse signal into a length, combining the branched optical signals provided with the optical path length difference, and branching, An optical multiplex communication method characterized in that after detecting the light intensity, the other is output to the other optical receiver.

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