JP2006238360A - Communication system, method, and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication system, communication method, and communication apparatus of an optical code multiplexed transmission scheme suppressing costs in a subscriber's house. <P>SOLUTION: A pulse generating unit 40 generates an optical pulse of a wavelength λ1, and a pulse generating unit 42 generates an optical pulse of a wavelength λ2. A wavelength selective light distribution unit 62 outputs the optical pulse of the wavelength λ1, in optical signals received via a transmission line 20, to a decoding unit 72 and outputs the optical pulse of the wavelength λ2 to an optical modulation unit 75. The optical modulation unit 75 performs light intensity modulation on the optical pulse of the wavelength λ2 based on a data train received from an encoding unit 74 and further, an optical encoder 76.1 converts the optical pulse into a light spreading code based on an orthogonal code sequence. An optical decoder 52.1 converts the light spreading code into an optical pulse based on the same orthogonal code sequence. A decoding unit 54 decodes the converted optical pulse into upstream data 1 and outputs the data. <P>COPYRIGHT: (C)2006,JPO&NCIPI

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 an optical code division multiplexing system.

  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 meet such a demand, FTTH (Fiber To The Home) service for connecting a subscriber to the Internet network via 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 as a double star network that is connected in a 1: n relationship. In providing the FTTH service, a double star network that requires less optical fiber installation is more cost effective.

  However, in a double star network, the base station is connected to the plurality of subscribers' homes using the same optical fiber. Therefore, the transmission data to each subscriber home and the reception data from each subscriber home are identified. There is a need to.

  Therefore, when data (hereinafter referred to as downlink data) is transmitted from the base station to each subscriber home, the base station transmits data to which each subscriber home identifier is added to all subscriber homes. At each subscriber's house, only the received downlink data with its own identifier added is extracted. When transmitting data (hereinafter referred to as uplink data) from each subscriber's home to the base station, each subscriber home first transmits a transmission request to the base station. Then, the base station gives transmission permission by controlling the transmission timing of each subscriber house. Each subscriber's house transmits the uplink data after the transmission permission is given.

  As described above, since the base station controls the transmission timing of each subscriber house, it is necessary to store information on the connected subscriber houses. For this reason, when the subscriber's home is added or changed, the information on the base station side must be changed, which is troublesome. Further, since a procedure for a transmission request and a transmission permission is necessary, there is a problem that a line utilization rate is reduced and a transmission rate of uplink data is limited.

  Therefore, data transmission by the optical code division multiplexing method is being studied. In the optical code division multiplexing method, the transmission side gives a predetermined optical phase difference based on an orthogonal code sequence to an optical signal, and transmits using an optical diffusion code spread in time. Then, the reception side restores the transmitted optical signal by performing the same processing as the transmission side.

  Furthermore, in the optical code division multiplexing method, due to the autocorrelation of the orthogonal code sequence, the transmission side and the reception side cannot be restored to an optical signal unless processing based on the same orthogonal code sequence is performed. Therefore, only an optical signal generated based on a specific orthogonal code sequence can be extracted and restored from a plurality of optical diffusion codes generated based on different orthogonal code sequences.

  Therefore, in the above-described double star network, even if each subscriber's home transmits an optical spreading code generated based on different orthogonal code sequences at any arbitrary timing, the base station is the same as each subscriber home. By performing each processing based on the orthogonal code sequence, it is possible to specify which subscriber's house is the data transmitted.

  Therefore, according to the optical code division multiplexing system, it is possible to simplify the management of the base station and improve the transmission rate of uplink data.

  Patent Document 1 discloses an optical code division multiplexing system that uses a duobinary code having three values “0”, “1”, and “−1” as a code sequence.

Patent Document 2 uses a first light intensity modulator that modulates light transmitted from a light source with transmission data, and a second light intensity modulator that has a higher modulation speed than the first light intensity modulator. An optical code multiplex transmission apparatus for generating an optical diffusion code is disclosed.
JP-A-10-164010 JP 2001-274770 A

  In a general optical communication system, an optical pulse having a binary light intensity is used as an optical signal. For example, if the bit rate of data to be transmitted is F [bit / sec], the time slot allocated to one optical pulse is 1 / F [sec].

  In the optical code division multiplexing method, an optical signal is spread in the time domain, and an optical phase difference is given according to the orthogonal code sequence. Therefore, a time diffusion width corresponding to the number of bits of the orthogonal code sequence is required. Therefore, when an optical signal composed of an optical pulse is converted into an optical diffusion code, the optical pulse expanded by time spreading must be prevented from overlapping the next time slot in order to avoid transmission errors.

  For example, when a 4-bit orthogonal code sequence (16 sequences) is used, it is necessary to spread four times in the time domain. Therefore, in order to fit an optical pulse spread four times in one time slot, the optical pulse width must be ¼ or less of the time slot. That is, in order to realize a transmission rate of 1 [Gbit / sec], the width of the optical pulse needs to be 250 [nsec] or less.

  However, a light source that generates a light pulse having a very short time width as described above is very expensive. For this reason, there is a problem that the cost at the subscriber's home increases and the cost reduction effect of laying the base station and the optical fiber by adopting the optical code division multiplexing system cannot be exhibited.

  Accordingly, the present invention has been made to solve such a problem, and an object of the present invention is to provide a communication system, a communication method, and a communication apparatus of an optical code multiplex transmission system that suppresses the cost at a subscriber's house. is there.

  According to the present invention, the transmission line, the first communication device that transmits the first optical signal via the transmission line, and the first optical signal received from the first communication device are used as the carrier wave. A second communication device that transmits one data to the first communication device, wherein the second communication device modulates the first optical signal with the first data; And a first optical code conversion means for converting the first optical signal modulated by the modulation means to an optical diffusion code, wherein the first communication device receives the optical diffusion code received from the second communication device. 1st optical code reverse conversion means to convert into 1 optical signal, and 1st decoding means to decode the 1st optical signal converted in the 1st optical code reverse conversion means into 1st data The communication system.

  Preferably, the first communication device combines the first and second optical signals with second modulation means for generating a second optical signal modulated with second data to be transmitted to the second communication device. Optical signal combining means for transmitting the optical signal, and the second communication device separates the first optical signal and the second optical signal received from the first communication device; And second decoding means for decoding the second optical signal into second data.

  Preferably, the second modulation unit generates a second optical signal having a wavelength different from that of the first optical signal, and the optical signal separation unit generates the first optical signal based on the wavelength of the received optical signal. The signal and the second optical signal are separated.

  Preferably, the second modulation unit generates a second optical signal having a transmission timing different from that of the first optical signal, and the optical signal separation unit generates the first optical signal based on the reception timing of the optical signal. The signal and the second optical signal are separated.

  Preferably, the first communication device includes an encoding unit that adds interpolation data so that the second data to be transmitted to the second communication device includes a predetermined carrier component, and the interpolation data is added by the encoding unit. And second modulation means for generating a first optical signal modulated with the second data, wherein the second communication device extracts a part of the first optical signal and converts it into the second data. Second decoding means for decoding is further included.

  Preferably, the first communication device further includes second optical code conversion means for converting the first optical signal into an optical diffusion code, and the second communication device receives the light diffusion received from the second communication device. Second optical code reverse conversion means for converting the code into the first optical signal is further included.

  Preferably, the first communication device performs data communication with at least one second communication device.

  According to the present invention, there is also provided a communication method between a first communication device and a second communication device connected via a transmission line, wherein the first communication device sends out a first optical signal. Using the first optical signal received by the second communication device from the first communication device as a carrier wave, and modulating the first data with the first data; and A first optical code conversion step of converting a first optical signal modulated with one data into an optical diffusion code and sending it, and an optical diffusion code received by the first communication device from the second communication device in the first A first optical code reverse conversion step for converting the optical signal into a first optical signal, and a first communication device for decoding the first optical signal converted in the first optical code reverse conversion step into first data A communication method comprising a decoding step.

  Preferably, the first communication device generates a second optical signal modulated with the second data, and the first communication device combines and transmits the first and second optical signals. An optical signal combining step, an optical signal separation step in which the second communication device separates the first optical signal and the second optical signal received from the first communication device, and a second communication device is the second And a second decoding step of decoding the optical signal into second data.

  Preferably, an encoding step in which the first communication device adds interpolation data so that the second data transmitted from the first communication device to the second communication device includes a predetermined carrier wave component; A second modulation step in which the first communication device modulates the second data with the interpolation data added to generate a first optical signal, and the second light received from the first communication device by the second communication device. And a second decoding step of extracting a part of the signal and decoding it into second data.

  Preferably, the first communication device performs data communication with at least one second communication device.

  In addition, according to the present invention, a communication device that performs data communication with another communication device via a transmission line, the first optical signal received from the other communication device is used as a carrier wave and modulated with transmission data. A communication device comprising: a modulating means for converting the first optical signal modulated with transmission data into an optical diffusion code and transmitting the optical signal.

  Preferably, the first optical signal and the second optical signal modulated by the transmission data from the other communication device are received from another communication device, and the first optical signal and the second optical signal are separated. Optical signal separation means and decoding means for decoding the second optical signal separated by the optical signal separation means into transmission data are further provided.

  According to the present invention, since the second communication device transmits data using the optical signal received from the first communication device as a carrier wave, the second communication device needs to include a carrier wave generating means. Absent. Therefore, even when the optical code division multiplexing system is realized, the second communication apparatus does not need to generate an optical pulse having a very short time width. Therefore, the second communication apparatus does not require an expensive light source, and can realize an optical code division multiplexing communication system and communication method with reduced costs.

  In addition, according to the present invention, since data is transmitted using an optical signal received from another communication apparatus as a carrier wave, it is not necessary to provide a carrier wave generating means. Therefore, it is not necessary to generate an optical pulse having a very short time width even when the optical code division multiplexing system is realized. Therefore, an expensive light source is not required, and a communication device that suppresses the cost for realizing the optical code division multiplexing system can be realized.

  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.

  Referring to FIG. 1, a communication system 100 includes a base station side device 1 and subscriber premises side devices 2.1, 2.2,. n, transmission lines 20 and 24, an optical distribution unit 22, and an optical coupling unit 26. The base station apparatus 1 includes a transmission unit 1.1 and a reception unit 1.2.

  The transmission unit 1.1 is connected to the subscriber premises equipment 2.1, 2.2,..., 2. from the Internet network or WAN (Wide Area Network) (not shown). An optical signal modulated with downlink data 1, 2,..., n to be transmitted to each of n is generated and transmitted via the transmission path 20. The transmission unit 1.1 includes an encoding unit 30, pulse generation units 40 and 42, 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 receives the subscriber home side devices 2.1, 2.2,. After adding an identifier for specifying n, it 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 pulse generator 40 generates an optical pulse having a wavelength λ1 that is a carrier wave of the downlink data 1, 2,..., N and outputs the optical pulse to the optical modulator 32. The pulse generator 40 generates an optical pulse having a bit rate capable of transmitting the entire downstream data 1, 2,..., N.

  The pulse generation unit 42 generates an optical pulse having a wavelength λ2 that is a carrier wave of the upstream data 1, 2,..., N and outputs the optical pulse to the optical coupling unit 34. The pulse generator 42 generates a light pulse having a pulse width that does not cause overlapping of time slots due to temporal diffusion and having coherence.

  Based on the data string received from the encoding unit 30, the optical modulation unit 32 modulates the optical intensity of the optical pulse output from the pulse generation unit 40. In the first embodiment, the light modulation unit 32 performs modulation so that the light intensity is zero or maximum, that is, “off” or “on”, corresponding to “0” or “1” of the data string. . Then, the optical modulation unit 32 outputs the modulated optical pulse to the optical coupling unit 34.

  The optical coupling unit 34 couples the optical pulse received from the optical modulation unit 32 and the optical pulse received from the pulse generation unit 42, and outputs them to the transmission path 20.

  The transmission path 20 is configured by an optical fiber, connects the base station side device 1 and the optical distribution unit 22, and transmits an optical signal transmitted from the base station side device 1 to the optical distribution unit 22.

  The optical distribution unit 22 divides the optical signal received via the transmission path 20 into n parts, and the divided optical signals are respectively connected to the subscriber premises devices 2.1, 2.2,. output to n.

  1. Subscriber premises equipment 2.1, 2.2,... n decodes the optical signal received from the base station side device 1 into downlink data 1, 2,. In addition, the subscriber premises equipment 2.1, 2.2,. n generates and transmits an optical signal modulated by uplink data 1, 2,..., n to be transmitted to the base station side apparatus 1.

  The subscriber premises apparatus 2.1 includes a wavelength selective light distribution unit 62, a decoding unit 72, an encoding unit 74, an optical modulation unit 75, and an optical encoder 76.1.

  The wavelength selective light distribution unit 62 divides the optical signal received via the transmission path 20 into two according to the wavelength. Then, the wavelength selective light distribution unit 62 outputs the optical pulse having the wavelength λ1 to the decoding unit 72 and outputs the optical pulse having the wavelength λ2 to the optical modulation unit 75.

  The decoding unit 72 generates a data string according to the light intensity of the optical pulse having the wavelength λ1 received from the wavelength selective light distribution unit 62. Then, the decoding unit 72 extracts only the data addressed to itself based on the identifier added to the generated data string, and outputs it as downlink data 1.

  The encoding unit 74 receives the uplink data 1 from the outside and encodes it into a binary data string composed of one-dimensional “0” and “1”. Then, the encoding unit 74 outputs the encoded data string to the optical modulation unit 75.

  Based on the data string received from the encoding unit 74, the light modulation unit 75 modulates the light intensity of the optical pulse having the wavelength λ 2 received from the wavelength selective light distribution unit 62. Then, the light modulation unit 75 outputs the light pulse whose light intensity has been modulated to the optical encoder 76.1. Hereinafter, since light modulator 75 is similar to light modulator 32, detailed description will not be repeated.

  The optical encoder 76.1 converts the optical pulse received from the optical modulation unit 75 into an optical diffusion code based on a predetermined orthogonal code sequence, and outputs the optical diffusion code to the optical coupling unit 26. In the following description, conversion to an optical diffusion code is also referred to as “optical code conversion”.

  Subscriber premises equipment 2.2, ..., 2. n are optical encoders 76.2, ..., 76, respectively, instead of the optical encoder 76.1. Except for the point that n is used, it is the same as subscriber premises apparatus 2.1, and therefore detailed description will not be repeated.

  The optical coupling unit 26 includes subscriber premises devices 2.1, 2.2,. The optical signals received from each of n are combined and output to the transmission line 24.

  The transmission path 24 is composed of an optical fiber, connects the base station side device 1 and the optical coupling unit 26, and transmits an optical signal received from the optical coupling unit 26 to the base station side device 1.

  The receiving unit 1.2 includes subscriber premises devices 2.1, 2.2,. The optical signals received from n are decoded into upstream data 1, 2,..., n, respectively, and output to the Internet network or WAN (not shown). The receiving unit 1.2 includes an optical distribution unit 50 and optical decoders 52.1, 52.2,. n and a decoding unit 54.

  The optical distribution unit 50 divides the optical signal received via the transmission path 24 into n, and the divided optical signals are optical decoders 52.1, 52.2,. output to n.

  Optical decoders 52. 1, 52. n converts the optical diffusion code received from the optical distribution unit 50 into an optical pulse based on a predetermined orthogonal code sequence, and outputs the optical pulse to the decoding unit 54. In the following description, conversion from an optical diffusion code to an optical pulse is also referred to as “optical code reverse conversion”.

  The decoding unit 54 includes optical decoders 52.1, 52.2,. The light intensity of the light pulse received from each of n is integrated for each time slot, and a binary data string of “0” or “1” is obtained based on whether the value is equal to or greater than a predetermined threshold value. Generate. Then, the decoding unit 54 decodes the generated data string into uplink data 1, 2,.

  As described above, in the optical code division multiplexing method, the optical encoder and the optical decoder need to perform the same processing. Therefore, the optical encoder 76.1 and the optical decoder 52.1 have the same configuration. Furthermore, optical encoders 76.2,. n and optical decoders 52. Each of n has the same configuration.

  FIG. 2 is a schematic configuration diagram of the optical encoder 76.1.

  Referring to FIG. 2, the optical encoder 76.1 includes an optical distribution unit 90, an optical coupling unit 92, and optical delay paths 94.1, 94.2, 94.3, 94.4.

  The optical distribution unit 90 equally distributes the optical pulses given from the outside into four, and outputs them to the optical delay paths 94.1, 94.2, 94.3, 94.4, respectively.

  The optical delay path 94.1 outputs the optical pulse received from the optical distribution unit 90 to the optical coupling unit 92 without delay.

  The optical delay path 94.2 delays the optical pulse received from the optical distribution unit 90 by the time of the pulse width and outputs the optical pulse to the optical coupling unit 92.

  The optical delay path 94.3 delays the optical pulse received from the optical distribution unit 90 by a time that is twice the pulse width and outputs the optical pulse to the optical coupling unit 92.

  The optical delay path 94.4 delays the optical pulse received from the optical distribution unit 90 by a time three times the pulse width and outputs the optical pulse to the optical coupling unit 92.

  Further, since the optical signal is a “transverse wave” that vibrates perpendicular to the traveling direction, an optical phase difference occurs when observed at two different points in the traveling direction. Therefore, an optical phase difference corresponding to the transmission path length occurs between the optical signal input to the transmission path and the optical signal output from the transmission path.

  Therefore, in the optical delay paths 94.1, 94.2, 94.3, and 94.4, the optical phase of the input optical signal and the output optical signal is in phase or in accordance with the orthogonal code sequence, respectively. The transmission path length is set so as to be in reverse phase, that is, “0” or “π”.

  The length required to delay the optical signal by the time of the pulse width is on the order of several centimeters, whereas the length required to invert the phase of the optical signal is on the order of several μm. . Therefore, since there is a difference of 10 6 between the two, a desired delay time and optical phase difference can be given by adjusting the length of the transmission line.

  The optical coupling unit 92 couples the optical pulses output from the optical delay paths 94.1, 94.2, 94.3, 94.4.

  The optical decoder 52.1 is the same as the optical encoder 76.1.

  Furthermore, optical encoders 76.2,. n and optical decoders 52. Since n is the same as that of optical encoder 76.1, detailed description will not be repeated.

  FIG. 3 is a diagram for explaining data transmission by the optical code division multiplexing method from the subscriber premises apparatus 2.1 to the base station apparatus 1 in the communication system 100.

  FIG. 3A shows an optical pulse output from the optical modulator 75.

  FIG. 3B shows an optical diffusion code after optical code conversion by the optical encoder 76.1.

  FIG. 3C shows an optical pulse after optical code reverse conversion by the optical decoder 52.1.

  FIG. 3D shows an optical signal input to the decoding unit 54.

  FIG. 3E shows an optical pulse after optical code reverse conversion by the optical decoder 52.2.

  FIG. 3F shows an optical signal input to the decoding unit 54.

  Referring to FIG. 3A, the optical modulation unit 75 transmits an optical pulse having a pulse width T received from the base station side device 1. The time slot Ts of the optical pulse is determined according to the bit rate of the uplink data 1.

  Referring to FIG. 3B, the optical encoder 76.1 has, for example, a 4-bit orthogonal code sequence “0101”, spreads the input optical pulse into four optical pulses, Optical phase differences of “0”, “π”, “0”, “π” are given.

  Referring to FIG. 3C, the optical decoder 52.1 has the same orthogonal code sequence “0101” as that of the optical encoder 76.1, and further receives the optical pulse received from the subscriber premises apparatus 2.1. The light is diffused into four optical pulses to give optical phase differences of “0”, “π”, “0”, and “π”, respectively. On the time axis, optical pulses having the same optical phase are intensified, and optical pulses having different optical phases are intensified. As a result, the optical decoder 52.1 outputs an optical signal having a light intensity characteristic as shown in FIG. Then, the decoding unit 54 integrates the light intensity for each time slot Ts to determine the presence or absence of an optical pulse.

  By the way, the optical signal transmitted from the subscriber premises apparatus 2.1 is transmitted to the other optical decoders 52.2,. Also distributed to n.

  Referring to FIG. 3 (e), the optical decoder 52.2 has, for example, an orthogonal code sequence “0000” different from that of the optical encoder 76.1, and receives an optical pulse received from the subscriber premises apparatus 2.1. Further, the light is diffused into four optical pulses to give optical phase differences of “0”, “0”, “0”, and “0”, respectively. As a result, the optical decoder 52.2 outputs an optical signal having a low level noise characteristic light intensity as shown in FIG.

  As described above, the base station side device 1 and the subscriber premises side devices 2.1, 2.2,. When n has different orthogonal code sequences, the optical signal cannot be restored normally. Therefore, data transmission is established only when the orthogonal code sequences are the same, and data transmission is not established when the orthogonal code sequences are different. Therefore, the uplink data 1 transmitted from the subscriber premises apparatus 2.1 does not affect the other uplink data 2,..., N in the base station apparatus 1.

  In the first embodiment, the optical modulation unit 75 realizes a first modulation unit, and optical encoders 76.1, 76.2,. n implements the first optical code conversion means, and optical decoders 52.1, 52.2,. n realizes a first optical code reverse conversion means, and the decoding unit 54 realizes a first decoding means. The optical modulation unit 32 implements a second modulation unit, the optical coupling unit 34 implements an optical signal coupling unit, the wavelength-selective optical distribution unit 62 implements an optical signal separation unit, and the decoding unit 72 2 decoding means is realized.

  According to the first embodiment of the present invention, the base station side apparatus outputs the optical pulse of wavelength λ1 modulated with downlink data and the optical pulse of wavelength λ2 that has not been modulated to the subscriber premises apparatus. To do. On the other hand, the subscriber premises equipment decodes the optical pulse of wavelength λ1 received from the base station side equipment into downlink data, modulates it with uplink data using the optical pulse of wavelength λ2 as a carrier wave, and further performs optical code conversion And then transmit to the base station side device. Therefore, since the subscriber premises apparatus does not require an expensive light source for generating an optical pulse that is a carrier wave, an optical code division multiplexing communication system with reduced costs can be realized.

  Further, according to the first embodiment of the present invention, data transmission is established only between an encoder and a decoder having the same structure. Therefore, line control such as transmission / reception timing between the base station side device and each of the plurality of subscriber side devices becomes unnecessary, and it becomes easy to cope with changes in subscribers.

[Embodiment 2]
In the first embodiment, the case where an optical pulse modulated by downlink data and an optical pulse serving as a carrier wave of uplink data are transmitted through the same transmission path using two different wavelengths has been described.

  On the other hand, in the second embodiment, a case will be described in which an optical pulse modulated with downlink data and an optical pulse serving as a carrier wave of uplink data are transmitted on the same transmission path using two different transmission timings.

  FIG. 4 is a schematic configuration diagram of a communication system 102 according to the second embodiment of the present invention.

  4, the communication system 102 includes a base station side device 3 and subscriber home side devices 4.1, 4.2,. n, transmission lines 20 and 24, an optical distribution unit 22, and an optical coupling unit 26. The base station side device 3 includes a transmission unit 3.1 and a reception unit 1.2.

  The transmission unit 3.1 is connected to the subscriber premises apparatus 4.1, 4.2,..., 4. from the Internet network or WAN (not shown). An optical signal modulated with downlink data 1, 2,..., n to be transmitted to each of n is generated and transmitted via the transmission path 20. The transmission unit 3.1 includes an encoding unit 30, a pulse generation unit 36, a pulse multiplication unit 38, an optical modulation unit 32, and an optical coupling unit 34.

  Since encoding unit 30 and optical modulation unit 32 are the same as those in the first embodiment, detailed description will not be repeated.

  The pulse generator 36 generates optical pulses that are carriers of downstream data 1, 2,..., N and upstream data 1, 2,. Further, the pulse generator 36 generates an optical pulse having a pulse width that does not cause overlap due to temporal diffusion associated with optical code conversion and having coherence. Then, the pulse generator 36 outputs the generated optical pulse to the pulse multiplier 38 and the optical coupler 34.

  The pulse multiplier 38 generates an optical pulse having a bit rate capable of transmitting the entire downlink data 1, 2,..., N, so that the number of optical pulses received from the pulse generator 36 is multiplied by an integer. Then, the pulse multiplier 38 outputs the optical pulse to the optical modulator 32.

  The optical coupling unit 34 couples the optical pulse received from the optical modulation unit 32 and the optical pulse received from the pulse generation unit 36, and outputs them to the transmission path 20.

  Since transmission line 20 and light distribution unit 22 are the same as those in the first embodiment, detailed description will not be repeated.

  Subscriber premises equipment 4.1, 4.2,. n decodes the optical signal received from the base station side device 3 into downlink data 1, 2,. Further, the subscriber premises equipment 4.1, 4.2,. n generates and transmits an optical signal modulated by uplink data 1, 2,..., n to be transmitted to the base station side device 3.

  The subscriber premises apparatus 4.1 includes an optical distribution unit 60, optical switches 64 and 66, a synchronization control unit 70, a decoding unit 73, an encoding unit 74, an optical modulation unit 75, and an optical encoder 76. 1 and.

  The optical distribution unit 60 divides the optical signal received via the transmission path 20 into two and outputs it to the optical switches 64 and 66.

  The optical switches 64 and 66 transmit or block the optical signal according to a control command from the synchronization control unit 70. Then, the optical switch 64 outputs the transmitted optical signal to the decoding unit 72. The optical switch 66 outputs the transmitted optical signal to the optical modulation unit 75.

  The decoding unit 73 generates a data string according to the light intensity of the optical signal received from the optical switch 64. Then, based on the identifier added to the generated data string, the decoding unit 73 extracts only the data addressed to itself and outputs it as downlink data 1. Similarly to the decoding units 72 and 54 in the first embodiment, the decoding unit 73 includes an opto-electric conversion unit (O / E) 68 that converts an optical signal into an electric signal corresponding to the light intensity.

  The photoelectric conversion unit 68 converts the optical signal received from the optical switch 64 into an electrical signal corresponding to the light intensity, and outputs it to a decoding circuit (not shown) included in the decoding unit 73 and also outputs it to the synchronization control unit 70. To do.

  Based on the electrical signal received from the photoelectric converter 68, the synchronization controller 70 is an optical pulse modulated by the downlink data 1, 2,..., N included in the optical signal received from the transmitter 3.1. And the reception timing of the optical pulse that is the carrier wave of the upstream data 1, 2,..., N is acquired. Then, the synchronization control unit 70 drives the optical switch 64 or / and 66 according to the reception timing to separate the optical pulse. That is, the synchronization control unit 70 outputs the optical pulse modulated by the downlink data 1, 2,..., N to the decoding unit 73, and the optical pulse that is the carrier wave of the uplink data 1, 2,. Is output to the light modulator 75. As described above, the optical pulse modulated by the downlink data 1, 2,..., N is obtained by multiplying the optical pulse that is the carrier wave of the uplink data 1, 2,. In this case, optical pulses that are carriers of upstream data 1, 2,..., N periodically appear in the optical pulses modulated by downstream data 1, 2,.

  Since encoding unit 74, optical modulation unit 75, and optical encoder 76.1 are the same as those in the first embodiment, detailed description thereof will not be repeated.

  Subscriber premises equipment 4.2,... n are optical encoders 76.2, ..., 76, respectively, instead of the optical encoder 76.1. Except for the point that n is used, it is similar to the subscriber premises apparatus 4.1, and therefore detailed description will not be repeated.

  Since optical coupling unit 26 and transmission path 24 are the same as in the first embodiment, detailed description will not be repeated.

  Since receiving unit 1.2 is the same as that in the first embodiment, detailed description will not be repeated.

  In the second embodiment, the optical modulation unit 75 implements the first modulation means, and optical encoders 76.1, 76.2,. n implements the first optical code conversion means, and optical decoders 52.1, 52.2,. n realizes a first optical code reverse conversion means, and the decoding unit 54 realizes a first decoding means. The optical modulator 32 implements the second modulator, the optical coupler 34 implements the optical signal coupler, the optical distributor 60 and the optical switches 64 and 66 implement the optical signal separator, and the decoder 73 implement | achieves a 2nd decoding means.

  According to the second embodiment of the present invention, in addition to the effects of the first embodiment, since only one light source that generates an optical pulse in the base station side device is required, the cost of the base station side device can be suppressed. it can. Therefore, it is possible to realize an optical code division multiplexing communication system with further reduced costs.

[Embodiment 3]
In the first and second embodiments, the case where the subscriber side apparatus separates the optical pulse modulated by the downlink data from the optical pulse that becomes the carrier wave of the uplink data has been described.

  On the other hand, in the third embodiment, a case will be described in which an optical pulse modulated with downlink data is used as it is for a carrier wave of uplink data.

  FIG. 5 is a schematic configuration diagram of a communication system 104 according to the third embodiment of the present invention.

  5, the communication system 104 includes a base station side device 5 and subscriber home side devices 6.1, 6.2,. n, transmission lines 20 and 24, an optical distribution unit 22, and an optical coupling unit 26. The base station side device 5 includes a transmission unit 5.1 and a reception unit 5.2.

  The transmission unit 5.1 transmits the subscriber home side devices 6.1, 6.2,..., 6. from the Internet network or WAN (not shown). An optical signal modulated with downlink data 1, 2,..., n to be transmitted to each of n is generated and transmitted via the transmission path 20. The transmission unit 5.1 includes an encoding unit 44, a pulse generation unit 36, and an optical modulation unit 32.

  The encoding unit 44 receives the downlink data 1, 2,..., N from the outside, and receives the subscriber home side devices 6.1, 6.2,. After adding an identifier for specifying n, it is encoded into a binary data string composed of one-dimensional “0” and “1”. Then, the encoding unit 44 adds an interpolation bit to the encoded data string so that the occurrence probability of “1” in a predetermined time interval is constant. Further, the encoding unit 44 outputs the data string to which the interpolation bit is added to the optical modulation unit 32.

  Since pulse generation unit 36 and light modulation unit 32 are the same as those in the second embodiment, detailed description will not be repeated.

  Since transmission line 20 and light distribution unit 22 are the same as those in the first embodiment, detailed description will not be repeated.

  Subscriber premises equipment 6.1, 6.2,... n decodes the optical signal received from the base station side device 5 into downlink data 1, 2,. Further, the subscriber premises devices 6.1, 6.2,. n generates and transmits an optical signal modulated by uplink data 1, 2,..., n to be transmitted to the base station side device 5.

  The subscriber premises apparatus 6.1 includes an optical distribution unit 60, a decoding unit 78, an encoding unit 74, an optical modulation unit 75, and an optical encoder 76.1.

  The optical distribution unit 60 divides the optical signal received via the transmission path 20 into two and outputs it to the decoding unit 78 and the optical modulation unit 75.

  The decoding unit 78 generates a data string according to the light intensity of the light pulse received from the light distribution unit 60. Then, the decoding unit 78 removes the interpolation bits added to the generated data string, and generates a data string. Furthermore, the decoding unit 78 extracts only the data addressed to itself based on the identifier, and outputs it as downlink data 1.

  Since encoding unit 74, optical modulation unit 75, and optical encoder 76.1 are the same as those in the first embodiment, detailed description thereof will not be repeated.

  Subscriber premises equipment 6.2,. n are optical encoders 76.2, ..., 76, respectively, instead of the optical encoder 76.1. Except for the point that n is used, it is similar to the subscriber premises apparatus 6.1, and therefore detailed description will not be repeated.

  Since optical coupling unit 26 and transmission path 24 are the same as in the first embodiment, detailed description will not be repeated.

  The receiving unit 5.2 includes the subscriber premises devices 6.1, 6.2,. The optical signals received from n are decoded into upstream data 1, 2,..., n, respectively, and output to the Internet network or WAN (not shown). The receiving unit 5.2 includes an optical distribution unit 50 and optical decoders 52.1, 52.2,. n and a decoding unit 56.

  Optical distribution unit 50 and optical decoders 52.1, 52.2,. Since n is the same as in the second embodiment, detailed description will not be repeated.

  The decoding unit 56 includes optical decoders 52.1, 52.2,. The light intensity of the optical signal received from each of n is integrated for each predetermined time slot, and binary data of “0” or “1” is determined based on whether the value is equal to or greater than a predetermined threshold value. Generate a column. Then, the decoding unit 56 decodes the generated data string into uplink data 1, 2,..., N, respectively.

  FIG. 6 is a diagram for explaining data transmission by an optical pulse to which an interpolation bit is added in the communication system 104.

  FIG. 6A is an example of downlink data.

  FIG. 6B shows an optical pulse output from the optical modulator 32 upon receiving the downlink data shown in FIG.

  FIG. 6C shows an optical pulse that is modulated with upstream data in response to the optical pulse shown in FIG.

  Referring to FIG. 6A, encoding unit 44 receives downstream data 1, 2,..., N and encodes it to “10110011”, for example. Furthermore, as shown in FIG. 6B, the encoding unit 44 adds an interpolation bit for each bit included in the data string so that “1” always exists in one time slot. That is, when the data to be transmitted is “1”, the encoding unit 44 adds the interpolation bit “0” and converts it to “10”. When the data to be transmitted is “0”, an interpolation bit “1” is added and converted to “01”.

  Therefore, the pulse generator 36 generates an optical pulse having a bit rate that is twice or more that of the downlink data. In this way, the optical pulse to which the interpolation bit is added is used as a carrier wave for upstream data.

  That is, the light modulation unit 75 performs modulation according to the data string received from the encoding unit 74 on the optical pulse output from the light modulation unit 32. For example, when the encoding unit 74 outputs “01101001”, the light modulation unit 75 outputs an optical pulse as shown in FIG. The optical modulator 75 performs modulation at a bit rate that is ½ of the optical pulse output from the pulse generator 36.

  Further, since the optical pulse received by the decoding unit 56 includes an optical pulse in the first half or the second half of the time slot, the decoding unit 56 integrates the light intensity within the time slot to obtain “0” or “1”. Can be determined.

  In the third embodiment, the optical modulation unit 75 realizes the first modulation means, and optical encoders 76.1, 76.2,. n implements the first optical code conversion means, and optical decoders 52.1, 52.2,. n realizes a first optical code reverse conversion means, and the decoding unit 56 realizes a first decoding means. Also, the encoding unit 44 implements an encoding unit, the optical modulation unit 32 implements a second modulation unit, and the decoding unit 78 implements a second decoding unit.

  According to the third embodiment of the present invention, in addition to the effects in the first embodiment, the base station side device transmits an optical pulse including downlink data and a carrier wave, and the subscriber premises side device receives the received light. Downlink data is decoded from the pulse, and the optical pulse is directly used as a carrier wave. Therefore, the base station side device does not need to separate the optical pulse modulated by the downlink data from the optical pulse serving as a carrier wave, so that the configuration is simplified and the optical code division multiplexing communication with further reduced cost is performed. A system can be realized.

[Embodiment 4]
In the first to third embodiments, the case has been described in which the subscriber side apparatus multiplexes by extracting only the data addressed to itself based on the identifier added to the received data string.

  On the other hand, in the fourth embodiment, a case will be described in which an optical code division multiplexing transmission method is used for downlink data transmission.

  FIG. 7 is a schematic configuration diagram of a communication system 106 according to the fourth embodiment of the present invention.

  7, the communication system 106 includes a base station side device 7 and subscriber home side devices 8.1, 8.2,. n, transmission lines 20 and 24, an optical distribution unit 22, and an optical coupling unit 26. The base station side device 7 includes a transmission unit 7.1 and a reception unit 5.2.

  The transmission unit 7.1 sends the subscriber premises equipment 8.1, 8.2,..., 8. from the Internet network or WAN (not shown). An optical signal modulated with downlink data 1, 2,..., n to be transmitted to each of n is generated and transmitted via the transmission path 20. The transmission unit 7.1 includes an encoding unit 58, a pulse generation unit 36, an optical modulation unit 32, and optical encoders 46.1, 46.2,. n and the optical coupling unit 48.

  The encoding unit 58 receives the downlink data 1, 2,..., N from the outside and encodes them into a binary data string consisting of one-dimensional “0” and “1”. Hereinafter, since encoding unit 58 is similar to encoding unit 44, detailed description will not be repeated.

  Since pulse generation unit 36 and light modulation unit 32 are the same as those in the second embodiment, detailed description will not be repeated.

  Optical encoders 46.1, 46.2,. n converts each optical pulse received from the optical modulation unit 32 into an optical diffusion code based on a predetermined orthogonal code sequence, and outputs it to the optical coupling unit 48.

  The optical coupler 48 couples the optical signals received from the optical modulators 32 and outputs the optical signals to the transmission line 20.

  Since transmission line 20 and light distribution unit 22 are the same as those in the first embodiment, detailed description will not be repeated.

  Subscriber premises equipment 8.1, 8.2,. n decodes the optical signal received from the base station side device 7 into downlink data 1, 2,. In addition, the subscriber premises equipment 8.1, 8.2,. n generates and transmits an optical signal modulated by uplink data 1, 2,..., n to be transmitted to the base station side device 7.

  The subscriber premises apparatus 8.1 includes an optical decoder 82.1, an optical distribution unit 60, a decoding unit 78, an encoding unit 74, an optical modulation unit 75, and an optical encoder 76.1.

  The optical decoder 82.1 performs optical code reverse conversion on the optical pulse received from the optical distribution unit 22 based on a predetermined orthogonal code sequence, and outputs the result to the optical distribution unit 60. The optical encoder 76.1 has the same configuration as that of the optical decoder 52.1.

  The optical distribution unit 60 divides the optical signal received via the transmission path 20 into two and outputs it to the decoding unit 78 and the optical modulation unit 75.

  Decoding section 78, encoding section 74, optical modulation section 75, and optical encoder 76.1 are the same as those in the third embodiment, and thus detailed description will not be repeated.

  Subscriber premises equipment 8.2,. n are optical decoders 82.2,..., 82. n, and instead of the optical encoder 76.1, optical encoders 76.2,. Except for the point that n is used, it is the same as the subscriber premises apparatus 8.1, and therefore detailed description will not be repeated. Optical encoders 76.2, ..., 76. n are optical decoders 52.2,. n has the same configuration as each other.

  Since optical coupling unit 26 and transmission path 24 are the same as in the first embodiment, detailed description will not be repeated.

  Since receiving unit 5.2 is the same as that of the third embodiment, detailed description will not be repeated.

  In the fourth embodiment, the optical modulation unit 75 implements the first modulation means, and optical encoders 76.1, 76.2,. n implements the first optical code conversion means, and optical decoders 52.1, 52.2,. n realizes a first optical code reverse conversion means, and the decoding unit 56 realizes a first decoding means. Further, the encoding unit 58 realizes encoding means, the optical modulation unit 32 realizes second modulation means, and optical encoders 46.1, 46.2,. n realizes the second optical code conversion means, and optical decoders 82.1, 82.2,. n realizes the second optical code reverse conversion means, and the decoding unit 78 realizes the second decoding means.

  According to the fourth embodiment of the present invention, in addition to the effects in the first embodiment, the base station side device transmits the downlink data by the optical code division multiplexing method, so that each of the downlink data is transmitted independently of each other. it can. Therefore, it is only necessary to add an optical encoder to the increase in the downlink data series accompanying the increase in subscriber homes. Therefore, a more flexible communication system can be realized as compared with a case where all downlink data is encoded into a one-dimensional data string by a common encoding unit.

[Other forms]
In the first to fourth embodiments described above, the case where the base station side device and the subscriber side device are connected by two different transmission paths for uplink data and downlink data has been described. It is good also as a structure connected by one transmission line. Since the optical signal is a transverse wave, no interference occurs between two optical signals having different propagation directions. Therefore, bidirectional data transmission for upstream data and downstream data is possible using a common transmission path.

  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 according to Embodiment 1 of this invention. It is a schematic block diagram of an optical encoder. It is a figure explaining the data transmission by the optical code division multiplexing system from the subscriber premises apparatus in a communication system to a base station side apparatus. It is a schematic block diagram of the communication system according to Embodiment 2 of this invention. It is a schematic block diagram of the communication system according to Embodiment 3 of this invention. It is a figure explaining the data transmission by the optical pulse which added the interpolation bit in a communication system. It is a schematic block diagram of the communication system according to Embodiment 4 of this invention.

Explanation of symbols

1, 3, 5, 7 Base station side device, 1.1, 3.1, 5.1, 7.1 Transmitter, 1.2, 5.2 Receiver, 2.1, 2.2,.・, 2. n, 4.1, 4.2,... n, 6.1, 6.2,... n, 8.1, 8.2,... n Subscriber premises equipment,
20, 24 Transmission path, 22, 50, 60, 90 Optical distribution unit, 26, 34, 48, 92 Optical coupling unit, 30, 44, 58, 74 Encoding unit, 32, 75 Optical modulation unit, 36, 40, 42 pulse generator, 38 pulse multiplier, 46.1, 46.2,. n, 76.1, 76.2, ..., 76. n Optical encoder, 52.1, 52.2,. n, 82.1, 82.2, ..., 82. n optical decoder, 54, 56, 72, 73, 78 decoding unit, 62 wavelength selective light distributing unit, 64, 66 optical switch, 68 photoelectric conversion unit (O / E), 70 synchronization control unit, 94.1 94.2, 94.3, 94.4 Optical delay path, 100, 102, 104, 106 Communication system, T pulse width, Ts time slot, λ1, λ2 wavelength.

Claims (13)

A transmission line;
A first communication device for sending a first optical signal via the transmission line;
A second communication device that transmits first data to the first communication device using the first optical signal received from the first communication device as a carrier wave;
The second communication device is:
First modulation means for modulating the first optical signal with the first data;
First optical code conversion means for converting the first optical signal modulated by the first modulation means into an optical diffusion code,
The first communication device is:
First optical code reverse conversion means for converting the light spreading code received from the second communication device into the first optical signal;
And a first decoding unit that decodes the first optical signal converted by the first optical code inverse conversion unit into the first data. The first communication device is:
Second modulation means for generating a second optical signal modulated with second data to be transmitted to the second communication device;
Optical signal combining means for combining and transmitting the first and second optical signals,
The second communication device is:
Optical signal separating means for separating the first optical signal and the second optical signal received from the first communication device;
The communication system according to claim 1, further comprising: a second decoding unit that decodes the second optical signal into the second data. The second modulation means generates the second optical signal having a wavelength different from that of the first optical signal;
The communication system according to claim 2, wherein the optical signal separation unit separates the first optical signal and the second optical signal based on a wavelength of the received optical signal. The second modulation means generates the second optical signal having a transmission timing different from that of the first optical signal,
The communication system according to claim 2, wherein the optical signal separating unit separates the first optical signal and the second optical signal based on a reception timing of the optical signal. The first communication device is:
Encoding means for adding interpolation data so that the second data to be transmitted to the second communication device includes a predetermined carrier wave component;
A second modulation unit for generating a first optical signal modulated with the second data to which the interpolation data is added in the encoding unit;
The second communication device is:
The communication system according to claim 1, further comprising second decoding means for extracting a part of the first optical signal and decoding it into the second data. The first communication device further includes second optical code conversion means for converting the first optical signal into an optical diffusion code,
The communication according to claim 5, wherein the second communication device further includes second optical code reverse conversion means for converting the optical spreading code received from the second communication device into the first optical signal. system.   The communication system according to claim 1, wherein the first communication device performs data communication with at least one second communication device. A communication method between a first communication device and a second communication device connected via a transmission line,
The first communication device sending a first optical signal;
A first modulation step in which the second communication device uses the first optical signal received from the first communication device as a carrier wave and modulates it with first data;
A first optical code conversion step in which the second communication device converts the first optical signal modulated with the first data into an optical diffusion code and sends it out;
A first optical code reverse conversion step for converting the optical spreading code received by the first communication apparatus from the second communication apparatus into the first optical signal;
A communication method comprising: a first decoding step in which the first communication device decodes the first optical signal converted in the first optical code inverse conversion step into the first data. A second modulation step in which the first communication device generates a second optical signal modulated with second data;
An optical signal combining step in which the first communication device combines and transmits the first and second optical signals;
An optical signal separation step of separating the first optical signal and the second optical signal received by the second communication device from the first communication device;
The communication method according to claim 8, further comprising: a second decoding step in which the second communication device decodes the second optical signal into the second data. An encoding step in which the first communication device adds interpolation data so that the second data transmitted from the first communication device to the second communication device includes a predetermined carrier wave component;
A second modulation step in which the first communication device modulates the second data to which the interpolation data is added to generate a first optical signal;
9. The method further comprises a second decoding step in which the second communication device extracts a part of the first optical signal received from the first communication device and decodes it into the second data. The communication method described in 1.   The communication method according to claim 8, wherein the first communication device performs data communication with at least one second communication device. A communication device that performs data communication with another communication device via a transmission path,
Modulation means for modulating the transmission data using the first optical signal received from the other communication device as a carrier wave;
An optical code conversion means for converting the first optical signal modulated with the transmission data into an optical diffusion code and transmitting the optical signal. Upon receiving the first optical signal from the other communication device and the second optical signal modulated by the transmission data from the other communication device, the first optical signal and the second optical signal are obtained. Optical signal separating means for separating;
The communication apparatus according to claim 12, further comprising decoding means for decoding the second optical signal separated by the optical signal separation means into the transmission data.

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