JP2009005066A - Communication system, communication method, and communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication system capable of coping with high-speed communication while simplifying the configuration of a terminal side in a time division multiple access network. <P>SOLUTION: In the communication system 100, a base station device 1 transmits an optical data signal including downlink data 1, 2, to n, and a plurality of optical pulse signals for distinguishing these data mutually to a transmission path 20. The plurality of optical pulse signals have wavelengths λ1 to λn each. The wavelengths λ1 to λn are determined based on the wavelength dispersion characteristics of the inside of a pulse generation section 12 so that the plurality of optical pulse signals arrive at a repeating installation 2 sequentially at intervals equal to a time slot of the optical data signal. The repeating installation 2 uses the plurality of optical pulse signals to extract each of a plurality of downlink data from the optical data signal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a communication system, a communication method, and a communication apparatus, and more particularly to a communication system, a communication method, and a communication apparatus using time-division multiplexed optical signals.

  With the development of information technology in recent years, there is an increasing demand for a high-capacity and high-quality Internet environment at home. In order to respond to such a demand, FTTH (Fiber To The Home) service for connecting a subscriber's home to the Internet network through an optical fiber is rapidly spreading.

  The FTTH configuration uses a single star network that connects a base station and each subscriber's home with a dedicated optical fiber, and an optical fiber with one end branched into a plurality of base stations and a plurality of subscriber homes. It is classified into a double star network that is connected in one-to-n (n: plural). In providing the FTTH service, a double star network that requires less optical fiber installation is more cost effective. As for the latter, there is a PON (Passive Optical Network) in which one optical fiber is shared by a plurality of users. The PON is a star network in which an optical coupler is provided in the middle of an optical fiber to branch the transmission path into 2 to 32 lines.

  In a PON type optical network in which a base station side device (OLT: Optical Line Terminal) and n ONUs (Optical Network Units; also referred to as “optical line terminators”) are connected via optical fibers, A technology (GE-PON) for realizing the FTTH service is used. In GE-PON, the OLT specifies the data frame transmission timing to the ONU. The ONU transmits a data frame at a designated timing. As a result, a plurality of data respectively transmitted from a plurality of ONUs are time-division multiplexed and sent to the OLT. The above operation is specified in IEEE 802.3ah.

  The transmission rate in GE-PON is large enough to allow signal processing of electronic circuits. However, in order to cope with a larger transmission rate, processing with an optical signal is required. As an example of a technology that can respond to such a request, for example, Japanese translations of PCT publication No. 2000-513158 (Patent Document 1) sends a light pulse from a central office, and a transmitter provided at each node sends the light pulse. An optical TDMA (time division multiplexed) optical network is disclosed that modulates back to a central office.

  Further, for example, Japanese Patent No. 3549801 (Patent Document 2) discloses a technique of separating data (for example, a signal light pulse train exceeding 100 Gbit / second) transmitted from a base station by a terminal device. According to this document, the terminal apparatus generates a control optical pulse train whose bit phase is synchronized with the signal optical pulse train in order to extract desired data from the optical data signal from the base station.

Also, for example, Japanese Patent Application Laid-Open No. 2004-193666 (Patent Document 3) discloses an optical time division demultiplexing apparatus capable of performing time division demultiplexing with high accuracy on a time division multiplexed signal having a high transmission rate. . This apparatus includes intensity modulation means for modulating the intensity with the interval of the optical pulse as a period so that the peak coincides with the optical pulse to be extracted from the signal light, and the spectrum of the intensity-modulated signal light as the peak of the optical pulse increases. And an extraction means for extracting the expanded spectrum of the optical pulse to be extracted at a position where the expanded spectrum of the other optical pulse does not reach.
Special Table 2000-513158 Japanese Patent No. 3549801 JP 2004-193666 A

  The higher the transmission rate, the shorter the time slot assigned to the data when generating the time division multiplexed signal on the base station side. According to the conventional technique, the control signal for separating the time division multiplexed signal is generated by the receiving terminal. For this reason, an apparatus for performing signal processing at higher speed and with higher accuracy is required on the receiving terminal side. This makes it difficult to simplify the configuration on the receiving terminal side, which increases the cost of the entire system.

  An object of the present invention is to provide a communication system, a communication method, and a communication apparatus that can cope with high-speed communication while simplifying the configuration of a terminal side in a time division multiple access network.

  In summary, the present invention is a communication system, a transmission line, a first optical signal including a plurality of first data, and a plurality of second lights for distinguishing the plurality of first data from each other. A first communication device that sends a signal to a transmission line; a second communication device that receives the first optical signal and the plurality of second optical signals via the transmission line; A communication device. The first communication device sequentially assigns a plurality of first data to time slots to generate a first optical signal, and sends the first optical signal to the transmission line, and a plurality of first data And second sending means for generating and sending two optical signals. The plurality of second optical signals respectively have a plurality of different wavelengths. The plurality of wavelengths are determined so that the plurality of second optical signals sequentially arrive at the second communication device at intervals equal to the time slot based on the chromatic dispersion characteristics of the second transmission means.

  Preferably, the second transmission means includes a plurality of light generating means for emitting a plurality of light fluxes each having a plurality of wavelengths, a light coupling means for combining the plurality of light fluxes to output output light, and a time slot. A signal generating means for generating a reference signal having a period; a modulating means for modulating output light in accordance with the reference signal to output a plurality of second optical signals; and receiving from the modulating means based on its own chromatic dispersion characteristics Separating means for temporally separating the plurality of second optical signals and sending them to the transmission line.

  More preferably, the second communication device generates an optical interaction between the first optical signal and the plurality of second optical signals and outputs a plurality of third optical signals. Means, decoding means for decoding each of the plurality of first data based on the plurality of third optical signals, and data transmission means for transmitting an optical data signal including the plurality of second data to the first communication device Including. The first communication device further includes receiving means for receiving an optical data signal.

  More preferably, the second communication device delays the plurality of second optical signals and outputs them to the optical interaction generating unit, and detection means for detecting the intensity of each of the plurality of third optical signals. And a delay amount control means for controlling the delay amount in the delay means so that the intensity of each of the plurality of third optical signals is maximized in response to the detection result of the detection means.

  More preferably, the data transmission means generates an optical data signal by time-division multiplexing a plurality of second data using the plurality of second optical signals. The receiving means receives the optical data signal, determines the arrival timings of the plurality of second optical signals in the second communication device, and corresponds to the optical signal that requires adjustment of the arrival timing from among the plurality of light generating means. Wavelength adjusting means for specifying the light generating means and adjusting the wavelength of the light beam emitted from the corresponding light generating means is included.

  According to another aspect of the present invention, a first communication device that transmits a first optical signal including a plurality of data and a plurality of second optical signals for distinguishing the plurality of data from each other to a transmission line; A communication method between a second communication device that receives a first optical signal and a plurality of second optical signals via a transmission line and separates a plurality of data. The plurality of second optical signals respectively have a plurality of different wavelengths. In the communication method, a plurality of data are sequentially assigned to time slots to generate a first optical signal, the first optical signal is transmitted to a transmission line, and a plurality of second optical signals are generated in a lump. And a step of separating and transmitting a plurality of second optical signals using a separating means capable of separating a plurality of optical signals having different wavelengths based on their own chromatic dispersion characteristics. The plurality of wavelengths are determined so that the plurality of second optical signals sequentially arrive at the second communication device at intervals equal to the time slot based on the chromatic dispersion characteristics of the separating means.

  According to still another aspect of the present invention, a plurality of first optical signals including a plurality of data and a plurality of second optical signals for distinguishing the plurality of data from each other are received via a transmission line, A communication device that transmits a first optical signal and a plurality of second optical signals to a terminal device that separates data. The plurality of second optical signals respectively have a plurality of different wavelengths. The communication apparatus sequentially assigns a plurality of data to time slots to generate a first optical signal, and sends a first optical signal to the transmission line, and a plurality of second optical signals. And a second sending means for generating and sending it to the transmission line. The second sending means separates the plurality of second optical signals and sends them to the transmission line based on the chromatic dispersion characteristics of the optical signal generating means that collectively generates a plurality of second optical signals. Separating means. The plurality of wavelengths are determined so that the plurality of second optical signals sequentially arrive at the terminal device at intervals equal to the time slot based on the chromatic dispersion characteristics of the separating means.

  According to the present invention, it is possible to cope with high-speed communication while simplifying the configuration of the terminal side in the time division multiple access network.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the same or corresponding parts in the drawings are denoted by the same reference numerals and description thereof will not be repeated.

[Embodiment 1]
FIG. 1 is a schematic configuration diagram of a communication system 100 according to the first embodiment of the present invention. With reference to FIG. 1, a communication system 100 includes a base station side device 1, a relay device 2, and a transmission path 20. The relay device 2 is installed in, for example, an office building or a condominium, and a plurality of ONTs (Optical Network Terminals) are connected. However, ONT is not shown in FIG.

Base station apparatus 1 includes a transmission unit 1.1 and a pulse generation unit 12.
The transmission unit 1.1 receives downlink data 1, 2,..., N for transmission to the relay device 2 from an Internet network or a WAN (Wide Area Network) not shown. The transmission unit 1.1 implements the “first transmission unit” in the present invention. The transmission unit 1.1 generates and outputs an optical data signal obtained by time-division multiplexing downlink data 1, 2,.

  The transmission unit 1.1 includes an encoding unit 30, a light source 10, an optical modulation unit 32, and an optical coupling unit 34. The encoding unit 30 receives the downlink data 1, 2,..., N from the outside, and assigns the downlink data 1, 2,. Sequential assignment is encoded into a binary data string composed of one-dimensional “0” and “1”. Then, the encoding unit 30 outputs the encoded data string to the optical modulation unit 32.

  The light source 10 is constituted by a laser oscillator, for example, and generates laser light having a wavelength λ0 having a predetermined light intensity. The light source 10 outputs the generated laser light to the light modulation unit 32.

  Based on the data string received from the encoding unit 30, the optical modulation unit 32 modulates the intensity of the laser light output from the light source 10 to generate an optical data signal. For example, the light modulation unit 32 modulates the light intensity to be zero and maximum (that is, “off” or “on”) corresponding to “0” and “1” of the data string, respectively. In this way, the optical modulation unit 32 generates an optical data signal obtained by time-division multiplexing the downlink data 1, 2,. The optical modulation unit 32 outputs the generated optical data signal to the optical coupling unit 34.

  The pulse generator 12 implements the “second transmission means” in the present invention, and generates a plurality of optical pulse signals having different wavelengths. In the present embodiment, the pulse generator 12 generates n optical pulse signals each having wavelengths λ1 to λn. The pulse generator 12 outputs n optical pulse signals to the optical coupler 34.

  Each period of the plurality of optical pulse signals is the period of the downlink data in the optical data signal generated by the optical modulator 32, that is, until the allocation of the downlink data 1, 2,. It is equal to the time required.

  The optical coupling unit 34 combines the optical data signal received from the optical modulation unit 32 and the optical pulse signal received from the pulse generation unit 12, and sends them to the transmission line 20.

  The transmission line 20 is composed of an optical fiber. The optical data signal output from the base station side device 1 and a plurality of optical pulse signals (lights with wavelengths λ1 to λn) are sent to the relay device 2 via the transmission path 20.

  Here, the speed of light traveling through the substance varies depending on the wavelength of the light. This phenomenon is called chromatic dispersion. In the present embodiment, the wavelengths λ1 to λn are such that a plurality of optical pulse signals sequentially arrive at the repeater 2 at intervals equal to the time slot of the optical data signal based on the chromatic dispersion characteristics inside the pulse generator 12. Determined.

  The relay apparatus 2 decodes the optical data signal into downlink data 1, 2,..., N using a plurality of optical pulse signals. These data are respectively sent to n ONTs connected to the relay device 2.

  The repeater 2 includes a wavelength selective light distribution unit 62, a delay unit 84, an optical interaction generation unit 18, an optical demultiplexer 64, and a decoding unit 86.

  The wavelength selective light distribution unit 62 separates the optical data signal and the optical pulse signal received via the transmission line 20 according to the wavelength. The wavelength selective light distribution unit 62 outputs the optical data signal (wavelength λ 0) to the optical interaction generation unit 18 and outputs a plurality of optical pulse signals (wavelengths λ 1 to λn) to the delay unit 84.

  The delay unit 84 delays the plurality of optical pulse signals by a predetermined time. The delay time is determined so that the timing at which the optical pulse signal has the maximum intensity is synchronized with the time slot of the downlink data corresponding to the optical pulse signal in the optical data signal. The delay unit 84 outputs the delayed optical pulse signal to the optical interaction generator 18.

  The optical interaction generator 18 generates an interaction due to an optical nonlinear effect between the optical data signal and the optical pulse signal. In particular, the optical interaction generator 18 generates four-wave mixing (FWM: Four Wave Mixing), which is a kind of optical Kerr effect. For example, when an optical data signal and an optical pulse signal having a wavelength λ1 are input to the optical interaction generation unit 18, the optical interaction generation unit 18 determines the wavelength difference between the wavelength λ0 of the optical data signal and the wavelength λ1 of the optical pulse signal. Two new interaction lights having different wavelengths (λ0−Δλ) and (λ1 + Δλ) by Δλ (= | λ1-λ0 |) are output.

  Since the timing at which the optical pulse signal having the wavelength λ1 has the maximum intensity is synchronized with the time slot to which the downlink data 1 is assigned, in this case, the four-wave mixing occurs only during the period of the time slot to which the downlink data 1 is assigned. Become. Therefore, the optical interaction generator 18 outputs only the interaction light corresponding to the light intensity of the downlink data 1 in the optical data signal. In other words, the optical interaction generator 18 extracts an optical signal modulated with data 1 from the optical data signal by using the optical pulse signal with the wavelength λ1. Hereinafter, the optical signal extracted from the optical data signal is also referred to as a DEMUX signal (separated signal).

  A plurality of optical pulse signals are sequentially input to the optical interaction generator 18 at the same time interval as the time slot of the optical data signal. Therefore, the optical interaction generator 18 outputs a plurality of DEMUX signals corresponding to the downlink data 1, downlink data 2,..., Downlink data n.

  The optical demultiplexer 64 separates and outputs a plurality of DEMUX signals for each wavelength. The plurality of DEMUX signals are input to the decoding unit 86.

  The decoding unit 86 includes decoders 86.1 to 86. each provided corresponding to a plurality of DEMUX signals. n is included. Decoders 86.1 to 86. n generates a data string according to the light intensity of the corresponding DEMUX signal, and outputs the data string as downlink data. Decoders 86.1 to 86. Downlink data 1,..., downlink data n are output from n.

  FIG. 2 is a diagram showing a configuration example of the pulse generator 12 shown in FIG. Referring to FIG. 2, pulse generator 12 includes signal generator 51 and light sources 52.1, 52.2,. n, an optical multiplexer 54, an optical modulator 55, and a wavelength dispersive medium 56.

  The signal generator 51 generates a reference signal having a period (for example, on the order of GHz) equal to the period of the downlink data 1 in the optical data signal generated by the optical modulator 32 of FIG. Light sources 52.1, 52.2,. Each of n includes, for example, a semiconductor laser and generates laser light (light flux) having a predetermined light intensity. In addition, the light sources 52.1, 52.2,. The wavelengths of the laser beams emitted from n are λ1, λ2,.

  The optical multiplexer 54 includes light sources 52. 1, 52. Lights with different wavelengths input from n are multiplexed. Based on the reference signal from the signal generator 51, the optical modulator 55 modulates the light intensity output from the optical multiplexer 54 to generate a plurality of optical pulse signals each having wavelengths λ1 to λn. As described above, since the light output from the optical multiplexer 54 is modulated in this embodiment, a plurality of optical pulse signals can be generated in a lump. As a result, it is not necessary to provide a light modulation unit for each light source, and thus it is possible to generate a plurality of light pulse signals with a simple configuration.

  The plurality of optical pulse signals output from the optical modulation unit 55 pass through the wavelength dispersive medium 56 and are output to the transmission line 20 via the optical coupling unit 33. The plurality of optical pulse signals are temporally separated by the wavelength dispersion in the wavelength dispersive medium 56 (transmission speeds are different from each other). That is, the wavelength dispersive medium 56 realizes the “separating means” in the present invention. Further, the signal generator 51 and the light sources 52.1, 52.2,. n, the optical multiplexer 54, and the optical modulator 55 implement “optical signal generation means”.

  The wavelength dispersive medium 56 is, for example, an optical fiber, but is not particularly limited to an optical fiber.

  FIG. 3 is a schematic configuration diagram of the optical interaction generator 18 shown in FIG. Referring to FIG. 5, the optical interaction generator 18 includes an optical coupler 33, an optical amplifier 36, a highly nonlinear fiber 38, and an optical filter 40.

  The optical coupler 33 combines the optical data signal having the wavelength λ0 and the optical pulse signal having the wavelength λ1 and outputs the combined signal to the optical amplifier 36. The optical amplifier 36 amplifies the optical data signal and the optical pulse signal received from the optical coupling unit 33 so as to generate an optical nonlinear effect, and outputs the amplified signal to the highly nonlinear fiber 38.

  The highly nonlinear fiber 38 is made of a medium having a high nonlinear coefficient. The highly nonlinear fiber 38 has two new interactions of wavelength (λ0−Δλ) and wavelength (λ1 + Δλ) by four-wave mixing of an optical data signal of wavelength λ1 having a predetermined light intensity and an optical pulse signal of wavelength λ2. Generate light.

  The optical filter 40 receives the optical data signal, the optical pulse signal, and the two interaction lights output from the highly nonlinear fiber 38, blocks the optical data signal and the optical pulse signal (absorption, diffusion, etc.), and 2 One of the two interaction lights is allowed to pass. Then, the optical filter 40 outputs the passed interaction light as a DEMUX signal.

  FIG. 4 is a diagram for explaining the four-wave mixing in the optical interaction generator 18. FIG. 4A shows the frequency spectrum of the optical signal input to the optical interaction generator 18. FIG. 4B shows the frequency spectrum of the optical signal output from the highly nonlinear fiber 38. FIG. 4C shows the frequency spectrum of the optical signal output from the optical filter 40.

  Referring to FIG. 4A, the optical data signal (wavelength λ 0) and the optical pulse signal (wavelength λ 1) amplified to a predetermined light intensity by the optical amplifier 36 are input to the optical interaction generator 18.

  Referring to FIG. 4B, when the optical data signal and the optical pulse signal propagate through the highly nonlinear fiber 38, four-wave mixing occurs, and 2 having a wavelength separated by a wavelength difference Δλ between the optical data signal and the optical pulse signal. Two interaction lights are generated.

  Referring to FIG. 4C, the optical filter 40 passes only one of the optical data signal, the optical pulse signal and the two interaction lights, and outputs the light as a DEMUX signal. For example, the wavelength λ0 of the optical data signal is 1550 [nm], and the wavelength λ1 of the optical pulse signal is 1555 [nm].

FIG. 5 is a diagram for explaining data extraction in the relay device 2.
FIG. 5A shows a time waveform of the optical data signal output from the wavelength selective light distributor 62. Referring to FIG. 5A, the optical data signal has a light intensity corresponding to a binary data string consisting of “0” and “1”. Then, if the time interval of one time slot is t, the time T required for all the downlink data to make a round is T = t × 4.

  FIG. 5B shows a time waveform of the optical pulse signal having the wavelength λ 1 output from the wavelength selective light distributor 62. Referring to FIG. 5 (b), the optical pulse signal of wavelength λ1 transmitted from the base station side device 1 has a light intensity peak at every time T during which all the downlink data allocation is completed.

  FIG. 5C shows a time waveform of an optical pulse signal having a wavelength λ 1 applied to the optical interaction generator 18. Referring to FIG. 5C, the delay unit 84 converts the optical pulse signal having the wavelength λ1 by the delay time Td1 so that the intensity peak of the optical pulse signal is synchronized with the time slot to which the downlink data 1 is assigned. Delay. Since the period of the time slot to which downlink data 1 is assigned coincides with the period of the optical pulse signal, there is no need to adjust the delay time Td1 for each time slot.

  FIG. 5D shows a DEMUX signal output as downlink data 1 from the optical interaction generator 18. Referring to FIG. 5D, the optical interaction generator 18 outputs a DEMUX signal corresponding to the downlink data 1 in a period in which the light intensity peak of the optical pulse signal exists.

  FIG. 5E shows a time waveform of an optical pulse signal having a wavelength λ 2 applied to the optical interaction generator 18. Referring to FIG. 5E, the optical pulse signal with wavelength λ2 arrives at the optical interaction generator 18 with a delay of time Td2 from the optical pulse signal with wavelength λ1. The delay unit 84 delays the optical pulse signal having the wavelength λ2 by the delay time Td1, similarly to the optical pulse signal having the wavelength λ1.

  The optical pulse signal of wavelength λ2 arrives at the relay apparatus 2 with a delay of time interval t of the time slot from the time when the optical pulse signal of wavelength λ1 arrives at the relay apparatus 2. Therefore, the optical pulse signal of wavelength λ2 is a signal synchronized with the time slot to which downlink data 2 is assigned. The delay unit 84 delays the optical pulse signal having the wavelength λ2, thereby synchronizing the intensity peak of the optical pulse signal with the time slot to which the downlink data 2 is assigned.

  FIG. 5 (f) shows a DEMUX signal output as downlink data 2 from the optical interaction generator 18. Referring to FIG. 5 (f), similarly to FIG. 5 (d), the optical interaction generator 18 outputs a DEMUX signal corresponding to the downlink data 2 in a period in which the intensity peak of the optical pulse signal exists. .

FIG. 6 is a diagram for schematically explaining a time difference between a plurality of optical pulse signals.
FIG. 6A shows time waveforms of a plurality of optical pulse signals output from the optical modulation unit 55 of FIG. Referring to FIG. 6A, the plurality of optical pulse signals substantially overlap on the time axis. In FIG. 6A, the plurality of optical pulse signals are shown in a shifted manner so that the plurality of optical pulse signals can be easily distinguished.

  FIG. 6B shows time waveforms of a plurality of optical pulse signals output from the wavelength dispersive medium 56 of FIG. With reference to FIG. 6A and FIG. 6B, the plurality of optical pulse signals pass through the wavelength dispersive medium 56, whereby the interval between the plurality of optical pulse signals is widened. In order to show this point in an easy-to-understand manner, the positions on the time axis of the first (leftmost) pulse are the same in FIGS. 6 (a) and 6 (b).

  FIG. 6C shows a time waveform of the optical pulse signal input to the wavelength selective light distribution unit 62 of FIG. Referring to FIG. 6C, the time intervals of the plurality of optical pulse signals are expanded by passing the plurality of optical pulse signals through the transmission line 20. As in FIG. 6B, the position of the first (leftmost) pulse on the time axis is the same in FIGS. 6A and 6C.

  FIG. 6D shows a time waveform of the optical data signal input to the wavelength selective light distributor 62 shown in FIG. Referring to FIGS. 6D and 6C, the optical pulse signal of wavelength λ1 is synchronized with the time slot to which downlink data 1 is assigned. Similarly, the optical pulse signal with wavelength λ2, the optical pulse signal with wavelength λ3, and the optical pulse signal with wavelength λ4 are assigned to the time slot to which downlink data 2 is assigned, the time slot to which downlink data 3 is assigned, and downlink data 4 to assign. Each time slot is synchronized.

  The plurality of optical pulse signals shown in FIG. 6C are delayed by the delay time Td1 by the delay unit 84. This makes it possible to maximize the intensity of each of the plurality of DEMUX signals.

  In the present embodiment, a plurality of optical pulse signals sequentially arrive at the relay apparatus 2 with a time shift corresponding to the time slot corresponding to the optical data signal. This facilitates the separation of one optical data signal into a plurality of DEMUX signals in the relay device 2 (more specifically, the optical interaction generator 18). Further, according to the present embodiment, it is not necessary to adjust the delay time for each time slot.

  The communication system 100 according to the first embodiment will be comprehensively described again. In the communication system 100, the base station side apparatus 1 sends an optical data signal including downlink data 1, 2,... N and a plurality of optical pulse signals for distinguishing these data from each other to the transmission line 20. To do. The plurality of optical pulse signals have wavelengths λ1 to λn, respectively. The wavelengths λ1 to λn are determined based on the chromatic dispersion characteristics of the transmission line 20 so that a plurality of optical pulse signals sequentially arrive at the repeater 2 at intervals equal to the time slot of the optical data signal. The relay apparatus 2 separates a plurality of downlink data using a plurality of optical pulse signals.

  This eliminates the need for an optical pulse generator for separating the optical data signal on the optical signal repeater side. Therefore, according to the communication system of the present embodiment, the optical signal repeater can be realized at low cost.

  Furthermore, even if the communication speed in the time division multiple access network increases, the optical signal relay device may separate the optical data signal using a plurality of optical pulse signals transmitted from the base station side device. Therefore, according to the present embodiment, it is possible to cope with high-speed optical time division multiplexing transmission.

  The optical interaction generator 18 may be configured to include a semiconductor optical amplifier instead of the above-described highly nonlinear fiber.

(Modification 1)
FIG. 7 is a schematic configuration diagram of an optical interaction generator 19A according to the first modification of the first embodiment. Referring to FIG. 7, an optical interaction generator 19A is obtained by replacing the optical amplifier 36 and the highly nonlinear fiber 38 with a semiconductor optical amplifier 42 in the optical interaction generator 18 shown in FIG. Since optical coupling unit 34 and optical filter 40 have the same configuration and function as optical interaction generation unit 18, detailed description thereof will not be repeated hereinafter.

  The semiconductor optical amplifier 42 is an optical amplifier including semiconductor optical amplifiers (SOA: Semiconductor Optical Amplifiers), and increases the light intensity and at the same time causes an interaction due to an optical nonlinear effect. The types of semiconductors used for the semiconductor optical amplifier are, for example, InP, InGaAs, InGaAsP, and the like.

  According to the first modification, since the optical interaction generator 19A does not include a highly nonlinear fiber, the optical interaction generator 19A can be made more compact than the optical interaction generator 18 shown in FIG.

(Modification 2)
FIG. 8 is a schematic configuration diagram of an optical interaction generator 19B according to the second modification of the first embodiment. Referring to FIG. 8, the optical interaction generator 19B is also referred to as a nonlinear loop mirror. The optical interaction generator 19B includes optical branching portions 66 and 68 and a highly nonlinear fiber 38.

  The optical branching unit 68 has four ports. Two of the four ports are connected to both ends of the highly nonlinear fiber 72. The remaining two ports function as an input port that receives an optical data signal and an output port that outputs a DEMUX signal.

  The optical branching unit 66 is inserted between the optical branching unit 68 and the highly nonlinear fiber 38, receives an optical pulse signal, and sends it to the highly nonlinear fiber 72.

  The highly nonlinear fiber 72 is made of a medium having a high nonlinear coefficient, and changes the phase of the optical data signal by an optical nonlinear effect between the optical data signal having the wavelength λ0 and the optical pulse signal having the wavelength λ1.

  Hereinafter, the operation of the optical interaction generator 19B will be described. The optical branching unit 68 divides the received optical data signal into two, and outputs two optical data signals that propagate clockwise and counterclockwise, respectively. If no optical pulse signal is input, each optical data signal propagates through the highly nonlinear fiber 72 and then returns to the optical branching unit 68. Then, the two optical data signals interfere with each other at the optical branching unit 68 and cancel each other. Therefore, no optical signal is output from the optical branching unit 68.

  On the other hand, when an optical pulse signal is input to the highly nonlinear fiber 72 via the optical branching unit 66, the rotational phase of the optical data signal changes due to the optical nonlinear effect in the process of propagating through the highly nonlinear fiber 72. Therefore, the optical data signals do not cancel each other because the interference at the optical branching unit 68 is insufficient. Therefore, a DEMUX signal corresponding to the optical interaction between the optical data signal and the optical pulse signal is output from the optical branching unit 68. That is, specific data can be extracted from the optical data signal by synchronizing the time slot in the optical data signal with the optical intensity peak of the optical pulse signal and inputting it to the optical interaction generator 19A.

  According to the second modified example, since an optical interaction can be generated even with an optical signal having a low light intensity, it is not necessary to excessively amplify the optical signal. For this reason, even if a low-power optical amplifier is used, sufficient optical interaction can be generated. Therefore, it is possible to realize a light interaction generator having a more economical configuration.

(Modification 3)
FIG. 9 is a schematic configuration diagram of an optical interaction generator 19C according to the third modification of the first embodiment. Referring to FIG. 9, the optical interaction generator 19 </ b> C has a cross-absorption modulation (XAM) effect of an electroabsorption semiconductor optical modulator (hereinafter referred to as “EA modulator”). This is a light interaction generator that uses The optical interaction generator 19C includes an optical coupler 701, an EA modulator 706, and a filter 707.

  The optical data signal (signal light) having the wavelength λ1 and the optical pulse signal (optical timing pulse train) having the wavelength λ2 are combined by the optical coupler 701 and then supplied to one input / output end face of the EA modulator 706. Due to the mutual absorption modulation effect of the EA modulator, the optical timing pulse train of wavelength λ2 modulated by the signal light from one input / output end face of the EA modulator 706, and the signal light of wavelength λ1 affected by the optical timing pulse train Is output. By extracting light of wavelength λ2 by the filter 707, short pulse signal light corresponding to the data is output.

(Modification 4)
FIG. 10 is a schematic configuration diagram of an optical interaction generator 19D according to the fourth modification of the first embodiment. Referring to FIG. 10, the optical interaction generator 19D includes a directional coupler 702, an EA modulator 706, a filter 707, and an isolator 708.

  The optical data signal (signal light) is supplied to one input / output end face of the EA modulator 706 via the directional coupler 702. On the other hand, the optical pulse signal (optical clock pulse train) is supplied to the other input / output end face of the EA modulator 706. As a result, an optical clock pulse train modulated by the signal light is output from the one input / output end face of the EA modulator 706. This optical clock pulse train passes through the directional coupler 702 and the filter 707 and is output.

  Note that signal light whose intensity is modulated by the optical clock pulse train is output from the other input / output end face of the EA modulator 706, but the signal light is blocked by the isolator 708. This is because when such signal light is output, the signal light interferes with the optical clock pulse train and impairs the quality of the pulse train.

  Here, the EA modulator is originally a device that modulates the intensity of input light by utilizing the characteristic that the light absorption coefficient changes according to the applied electric field. However, the light absorption coefficient of the EA modulator also depends on the intensity of the input light. That is, the greater the intensity of input light, the smaller the amount of light absorbed by the EA modulator. And when the intensity | strength of input light is larger than predetermined value, the fall of light absorption amount is saturated. The EA modulator 706 in FIG. 10 regenerates signal light by utilizing this property.

  FIG. 11 is a conceptual diagram for explaining the operating principle of the EA modulator 706 of FIG. As shown in FIG. 11, the EA modulator 706 receives an optical clock pulse train from one input / output end face 801 and receives signal light from the other input / output end face 802.

  When ‘1’ of signal light (that is, a portion with high light intensity) is input from the input / output end face 802, the light absorption amount in the EA modulator 706 is saturated to the lowest level. Therefore, the optical clock pulses C1, C2, C4, C5 corresponding to “1” of the signal light are output from the input / output end face 802 without being absorbed so much.

  On the other hand, when ‘0’ of signal light (that is, a portion with low light intensity) is input from the input / output end face 802, the light absorption amount in the EA modulator 706 increases. Therefore, when ‘0’ is input, very large light absorption occurs with respect to the optical clock pulse. Therefore, the optical clock pulse C 3 corresponding to “0” of the signal light is converted into light having a very low intensity and output from the input / output end face 802.

  In this way, according to the configuration of FIG. 10, it is possible to operate as an optical interaction generator by receiving intensity modulation according to signal light.

[Embodiment 2]
Since the configuration of the communication system of the second embodiment is similar to that of communication system 100 shown in FIG. 1, the following description will not be repeated. In the communication system of the second embodiment, the optical signal repeater performs control so that the intensity of the DEMUX signal is maximized. For this reason, the first embodiment and the second embodiment are different in the part related to the control of the DEMUX signal in the optical signal repeater.

  FIG. 12 is a diagram for explaining a configuration of a part related to control of the DEMUX signal of the relay device 21 according to the second embodiment. Referring to FIG. 12, relay device 21 is a relay device used in communication system 100 in FIG. The relay device 21 differs from the relay device 2 in that a delay unit 84A is included instead of the delay unit 84. The relay device 21 is different from the relay device 2 in that it further includes an optical distribution unit 91, an intensity monitor unit 92, and a delay control unit 93. Since the configuration of other parts of relay device 21 is the same as the configuration of the corresponding portion of relay device 2, the following description will not be repeated.

  As in the first embodiment, the optical interaction generator 18 receives the optical data signal of wavelength λ0 and the plurality of optical pulse signals (wavelengths λ1 to λn) and outputs a plurality of DEMUX signals. The light distributor 91 distributes each of the plurality of DEMUX signals output from the optical interaction generator 18 into two. One and the other of the two distributed DEMUX signals are input to the decoding unit 86 and the intensity monitoring unit 92, respectively.

  The intensity monitor unit 92 monitors the intensity of the DEMUX signal and outputs the monitoring result to the delay control unit 93. The delay control unit 93 controls the delay unit 84A according to the monitoring result (the intensity of the DEMUX signal) of the intensity monitor unit 92. As a result, the delay time of the optical pulse signal of wavelength λ1 in the delay unit 84A changes. The delay control unit 93 controls the delay time of the optical pulse signal so that the intensity of the DEMUX signal indicated by the intensity monitor unit 92 is maximized. For example, the delay control unit 93 uniformly changes the delay amount for a plurality of pulse signals.

  In an ideal state, the timing at which the intensity of the optical pulse signal is maximized is synchronized with the time slot to which downlink data (for example, downlink data 1) is allocated in the optical data signal, so that the intensity of the DEMUX signal is always maximum. Become. However, for example, due to various factors such as fluctuations in the length of the transmission path due to temperature, a deviation may occur between the timing at which the intensity of the optical pulse signal is maximized and the time slot to which downlink data is assigned.

  According to the second embodiment, by controlling the delay time of the optical pulse signal according to the intensity of the DEMUX signal, when the decoding unit 86 decodes the data string according to the optical intensity of the DEMUX signal, the base station side It becomes possible to further improve the reproduction accuracy of the data string generated by the apparatus.

[Embodiment 3]
FIG. 13 is a schematic configuration diagram of a communication system 100A according to the third embodiment of the present invention. Referring to FIG. 13, communication system 100A includes base station side device 1A, transmission paths 20 and 24, and relay device 2A.

  The relay device 2A receives upstream data 1, upstream data 2,..., Upstream data n from n ONTs. The relay apparatus 2A transmits an optical data signal generated by time-division multiplexing n pieces of uplink data to the base station side apparatus 1A via the transmission line 24. The base station side device 1A decodes the optical data signal from the relay device 2A. In this respect, the communication system 100A is different from the communication system 100 according to the first embodiment. Next, a difference in configuration between the communication system 100A and the communication system 100 will be described.

  Referring to FIGS. 13 and 1, relay device 2 </ b> A relays in that it further includes an optical distribution unit 60, a filter 70, an encoding unit 74, an optical interaction generation unit 75, and an optical coupling unit 67. Different from device 2. The filter 70, the encoding unit 74, the optical interaction generation unit 75, and the optical coupling unit 67 implement the “data transmission unit” of the present invention.

  The optical distribution unit 60 distributes the plurality of optical pulse signals received from the delay unit 84 to the optical interaction generation unit 18 and the optical interaction generation unit 75. The filter 70 transmits an optical pulse signal having a predetermined wavelength (for example, wavelength λ1) among the plurality of optical pulse signals. In the following, it is assumed that the filter 70 outputs an optical pulse signal having the wavelength λ1.

  The encoding unit 74 receives upstream data 1, upstream data 2,..., Upstream data n from the outside, and each of these data is binary data composed of one-dimensional “0” and “1”. Encode to a column. Then, the encoding unit 74 generates an optical data signal corresponding to the encoded data string and outputs the optical data signal to the optical interaction generating unit 75. The encoding unit 74 includes encoders 74.1 to 74, which are provided corresponding to each of the uplink data 1, the uplink data 2,. n is included. Encoders 74.1 to 74. n encodes the corresponding upstream data and outputs an optical data signal.

  The optical interaction generator 75 includes encoders 74.1 to 74. n corresponding to the optical interaction generators 75.1 to 75. n is included. Optical interaction generator 75.1-75. Each of n has the same configuration as that of the optical interaction generator 18 shown in FIG. 3 (the configuration shown in FIG. 7 or FIG. 8 may be used).

  Optical interaction generator 75.1-75. n causes an optical interaction between the optical data signal from the corresponding encoder and the optical pulse signal of wavelength λ1. The optical coupling unit 67 includes optical interaction generators 75.1 to 75. A plurality of optical signals respectively output from n are combined and sent to the transmission line 24. The light interaction generators 75.1 to 75. The optical data signal sent to the base station side apparatus 1A is equivalent to a signal generated by time-division multiplexing upstream data 1, upstream data 2,.

  The base station apparatus 1A is different from the base station apparatus 1 in that it further includes a receiving unit 1.2. The receiving unit 1.2 includes a decoding unit 80. The decoding unit 80 converts the optical data signal received via the transmission path 24 into an electrical signal, and generates a binary data string “0” or “1”. And the decoding part 80 isolate | separates the produced | generated data sequence for every predetermined | prescribed time slot, decodes it to uplink data 1, 2, ..., n, and outputs it.

  According to the third embodiment, in addition to the effects of the first embodiment, data can be transmitted from relay apparatus 2A to base station side apparatus 1. Thus, according to the third embodiment, bidirectional optical time division multiplexing transmission can be realized.

[Embodiment 4]
FIG. 14 is a schematic configuration diagram of a communication system 100B according to the fourth embodiment of the present invention. Referring to FIGS. 14 and 13, communication system 100B includes communication system 100A in that base station side apparatus 1B is included instead of base station side apparatus 1A, and relay apparatus 2B is included instead of relay apparatus 2A. And different.

  The base station side device 1B is different from the base station side device 1A in that the receiving unit 1.2 further includes an optical distribution unit 35 and a wavelength control unit 14. The relay device 2B is different from the relay device 2A in that an optical demultiplexer 76 is included instead of the filter 70. The optical demultiplexer 76, the encoding unit 74, the optical interaction generation unit 75, and the optical coupling unit 67 implement the “data transmission unit” of the present invention.

  The configuration of other parts of the communication system 100B is the same as the configuration of the corresponding part of the communication system 100A.

  In the repeater 2B, the optical demultiplexer 76 separates the plurality of optical pulse signals received from the optical distribution unit 60 for each wavelength. The plurality of optical pulse signals are converted into optical interaction generators 75.1-75. Each is input to n.

  In the base station side apparatus 1B, the optical distribution unit 35 distributes the optical data signal received from the transmission path 24 to the decoding unit 80 and the wavelength control unit 14. The wavelength control unit 14 receives the optical data signal from the optical distribution unit 35, and determines the arrival timing of the plurality of optical pulse signals in the relay apparatus 2B. Specifically, the wavelength control unit 14 determines whether or not two data in the data sequence included in the optical data signal overlap in time.

  That two data in the optical data signal overlap in time means that two of the plurality of optical pulse signals sent from the base station side apparatus 1B to the relay apparatus 2B overlap in time. . When two data in the optical data signal are overlapped, the wavelength control unit 14 specifies an optical pulse signal whose arrival timing is shifted among the plurality of optical pulse signals based on the two data. Then, the wavelength controller 14 outputs a signal SW for controlling the wavelength of the optical pulse signal to the pulse generator 12. The pulse generator 12 receives the signal SW and changes the wavelength of the optical pulse signal.

  FIG. 15 is a diagram for explaining control of the pulse generator 12 by the wavelength controller 14 of FIG. Referring to FIG. 15, wavelength control unit 14 outputs a signal SW including signals SW1, SW2,. Light sources 52.1, 52.2,. n changes the wavelength of the output light when it receives signals SW1, SW2,..., SWn, respectively.

  For example, the light sources 52.1, 52.2,. Each of n includes a semiconductor laser, a Peltier element that changes the temperature of the semiconductor laser in contact with the semiconductor laser, and a voltage control unit that controls an applied voltage of the Peltier element. The voltage control unit changes the applied voltage of the Peltier element according to the signal from the wavelength control unit 14. As a result, the wavelength of the laser light emitted from the semiconductor laser changes.

  As described above, according to the fourth embodiment, the wavelength control unit 14 receives the optical data signal from the relay apparatus 2B and determines the arrival timing of the plurality of optical pulse signals in the relay apparatus 2B. The wavelength control unit 14 includes light sources 52.1, 52.2,. From n, the light source corresponding to the optical pulse signal that needs to be adjusted for the timing of arrival at the relay apparatus 2B is specified. The wavelength control unit 14 adjusts the wavelength of the light beam emitted from the light source. Thereby, the time interval of the plurality of optical pulse signals arriving at the relay device 2B can be kept at the time slot interval of the optical data signal transmitted from the base station side device 1B. Therefore, the relay apparatus 2B can accurately separate the optical data signal transmitted from the base station side apparatus 1B into n pieces of data. Further, the base station apparatus 1B can correctly decode the uplink data 1, 2,..., N based on the optical data signal received from the relay apparatus 2B.

  In this configuration, the optical fiber 20 and the optical fiber 24 are combined into one by connecting the base station side device and the relay device via an optical directional coupler (bidirectional with a single optical fiber). Obviously, it is possible to transmit).

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

It is a schematic block diagram of the communication system 100 according to Embodiment 1 of the present invention. It is a figure which shows the structural example of the pulse generation part 12 shown in FIG. It is a schematic block diagram of the optical interaction generation | occurrence | production part 18 shown in FIG. It is a figure explaining 4 light wave mixing in the optical interaction generation part. It is a figure explaining extraction of the data in the relay apparatus 2. FIG. It is a figure for demonstrating typically the time difference of a several optical pulse signal. It is a schematic block diagram of the optical interaction generation part 19A according to the modification 1 of Embodiment 1. FIG. It is a schematic block diagram of the optical interaction generation part 19B according to the modification 2 of Embodiment 1. FIG. It is a schematic block diagram of the optical interaction generation part 19C according to the modification 3 of Embodiment 1. FIG. It is a schematic block diagram of optical interaction generation part 19D according to the modification 4 of Embodiment 1. FIG. It is a conceptual diagram for demonstrating the operation principle of the EA modulator 706 of FIG. It is a figure explaining the structure of the part relevant to control of the DEMUX signal of the relay apparatus 21 which concerns on Embodiment 2. FIG. It is a schematic block diagram of the communication system 100A according to Embodiment 3 of the present invention. It is a schematic block diagram of the communication system 100B according to Embodiment 4 of this invention. It is a figure for demonstrating control of the pulse generation part 12 by the wavelength control part 14 of FIG.

Explanation of symbols

  1, 1A, 1B Base station side device, 2, 2A, 2B, 21 relay device, 1.1 transmitting unit, 1.2 receiving unit, 10, 52.1 to 52. n light source, 12 pulse generation unit, 14 wavelength control unit, 18, 19A to 19D, 75 optical interaction generation unit, 20, 24 transmission path, 30, 74 encoding unit, 32, 55 optical modulation unit, 33, 34, 67 optical coupling unit, 35, 60, 91 optical distribution unit, 36 optical amplifier, 38, 72 highly nonlinear fiber, 40 optical filter, 42 semiconductor optical amplifier, 51 signal generation unit, 54 optical multiplexer, 56 wavelength dispersive medium, 62 wavelength selective light distribution unit, 64,76 optical demultiplexer, 66,68 optical branching unit, 70 filter, 74.1-74. n encoder, 75.1-75. n Optical interaction generator, 80,86 decoding unit, 84,84A delay unit, 86.1-86. n decoder, 92 intensity monitor unit, 93 delay control unit, 100, 100A, 100B communication system, 701 optical coupler, 702 directional coupler, 706 EA modulator, 708 isolator, 801, 802 input / output end face, C1-C5 Optical clock pulse.

Claims (7)

A transmission line;
A first communication device that sends a first optical signal including a plurality of first data and a plurality of second optical signals for distinguishing the plurality of first data from each other to the transmission line;
A second communication device that receives the first optical signal and the plurality of second optical signals via the transmission path and separates the plurality of first data;
The first communication device is:
First sending means for sequentially assigning the plurality of first data to time slots to generate the first optical signal and sending the first optical signal to the transmission line;
Second sending means for generating and sending the plurality of second optical signals,
The plurality of second optical signals respectively have a plurality of different wavelengths.
The plurality of wavelengths are determined so that the plurality of second optical signals sequentially arrive at the second communication device at intervals equal to the time slot based on chromatic dispersion characteristics of the second transmission means. ,Communications system. The second delivery means includes
A plurality of light generating means for emitting a plurality of light beams each having the plurality of wavelengths;
Optical coupling means for coupling the plurality of light beams and outputting output light;
Signal generating means for generating a reference signal having a period corresponding to the time slot;
Modulation means for modulating the output light according to the reference signal and outputting the plurality of second optical signals;
2. The communication system according to claim 1, further comprising: a separation unit that temporally separates the plurality of second optical signals received from the modulation unit based on its own chromatic dispersion characteristics and sends the second optical signal to the transmission path. The second communication device is:
Optical interaction generating means for generating an optical interaction between the first optical signal and the plurality of second optical signals and outputting a plurality of third optical signals;
Decoding means for respectively decoding the plurality of first data based on the plurality of third optical signals;
Data transmitting means for transmitting an optical data signal including a plurality of second data to the first communication device,
The communication system according to claim 2, wherein the first communication device further includes receiving means for receiving the optical data signal. The second communication device is:
Delay means for delaying the plurality of second optical signals to output to the optical interaction generating means;
Detecting means for detecting the intensity of each of the plurality of third optical signals;
4. The apparatus according to claim 3, further comprising: a delay amount control unit that receives a detection result of the detection unit and controls a delay amount in the delay unit so that each of the plurality of third optical signals has a maximum intensity. The communication system described. The data transmission means generates the optical data signal by time division multiplexing the plurality of second data using the plurality of second optical signals,
The receiving means includes
Receiving the optical data signal, determining the arrival timing of the plurality of second optical signals in the second communication device, and corresponding to the optical signal that requires adjustment of the arrival timing from the plurality of light generation means The communication system according to claim 3, further comprising: a wavelength adjusting unit that identifies a light generating unit that adjusts a wavelength of a light beam emitted from the corresponding light generating unit. A first communication device that sends a first optical signal including a plurality of data and a plurality of second optical signals for distinguishing the plurality of data from each other to a transmission line; and A communication method between a second communication device that receives a first optical signal and the plurality of second optical signals and separates the plurality of data,
The plurality of second optical signals respectively have a plurality of different wavelengths.
The communication method is:
Sequentially assigning the plurality of data to time slots to generate the first optical signal, and sending the first optical signal to the transmission path;
Collectively generating the plurality of second optical signals;
Separating the plurality of second optical signals using a separating means capable of separating a plurality of optical signals having different wavelengths from each other based on their own chromatic dispersion characteristics,
The plurality of wavelengths are determined such that the plurality of second optical signals sequentially arrive at the second communication device at an interval equal to the time slot based on chromatic dispersion characteristics of the separating means. . A terminal device that receives a first optical signal including a plurality of data and a plurality of second optical signals for distinguishing the plurality of data from each other via a transmission line and separates the plurality of data A communication device for transmitting the first optical signal and the plurality of second optical signals,
The plurality of second optical signals respectively have a plurality of different wavelengths.
The communication device
First sending means for sequentially assigning the plurality of data to time slots to generate the first optical signal and sending the first optical signal to the transmission line;
A second sending means for sending the plurality of second optical signals to the transmission line;
The second delivery means includes
Optical signal generating means for collectively generating the plurality of second optical signals;
Separating means for separating the plurality of second optical signals based on their chromatic dispersion characteristics and sending them to the transmission line;
The plurality of wavelengths are determined such that the plurality of second optical signals sequentially arrive at the terminal device at an interval equal to the time slot based on a wavelength dispersion characteristic of the separating unit.

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