JP2006165823A - Light transmission method and system and light transmitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce cross-talk from a digital data signal to an analog broadcasting signal in a wavelength division multiplex light transmission system. <P>SOLUTION: A block dividing circuit 18 blocks a digital data signal, and supplies it to randomizers 20 and 22. The randomizers 20 and 22 respectively randomize input data by bit units according to different random number sequences. Then, FFT 24 and 26 operate the high speed Fourie-transformation of the output data of the randomizers 20 and 22. A switch control circuit 28 decides which of the outputs of the randomizers 20 and 22 is more difficult to collide with the frequency components of an analog television signal by referring to an analog television signal frequency table 30, and controls a switch 36 according to the result. An electricity/light converter 38 converts the output of a switch 36 into an optical signal whose wavelength is λ2. A light multiplexing device 40 multiplexes an analog television signal light from the electricity/light converter 16 to the output signal light of the electricity/light converter 38. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical transmission method and system for transmitting a digital data signal and an analog broadcast signal by wavelength multiplexing using an optical fiber, and an optical transmitter.

  In an optical transmission system in which an optical fiber is used to wavelength-multiplex and transmit digital data signals and analog broadcast signals, so-called analog television signals, multi-channel analog television signals are originally converted into one channel, that is, one wavelength optical analog signal. After batch conversion, it is multiplexed with the digital data signal.

  In order to maintain a good image quality, the optical analog signal needs to maintain a high code-to-noise ratio (CNR). Therefore, the optical analog signal is transmitted to the optical fiber with a light intensity that is about 10 dB higher than the data signal transmitted in the same optical fiber at a different wavelength. For example, the transmission intensity of the optical data signal is about +4 dBm, whereas the optical analog signal is transmitted at about +15 dBm.

  When a digital data signal has a high power component at the frequency used in an analog television signal, it is a video channel that uses the frequency component of the analog television signal, resulting from the nonlinear effect of optical fibers (mainly induced Raman effect) Image quality degradation occurs (see Non-Patent Document 1).

As means for solving this problem, Patent Documents 1 and 2 describe a configuration using a specific optical fiber and wavelength arrangement.
F. Coppinger, et al., “Nonlinear Raman Cross-Talk in a Video Overlay Passive Optical Network,” OFC2003, TuR5, (2003) JP 2000-244404 A JP 2004-166300 A

  Since the methods described in Patent Documents 1 and 2 do not dramatically reduce the nonlinear effect of the optical fiber, the effect is limited. In particular, when the digital data signal is a repetition of a specific bit string having a short code length, the digital data signal has a high power component at a specific frequency. When the specific frequency is used in an analog television signal, even if the methods described in Patent Documents 1 and 2 are adopted, the image quality of the image of the analog television signal is greatly adversely affected. For example, an idle code consisting of 20 bits defined by Ethernet (registered trademark) is repeatedly transmitted during a period in which there is no data signal, and thus has a high power component at a specific frequency.

  It is an object of the present invention to provide an optical transmission method and system and an optical transmission apparatus that can eliminate such disadvantages.

  According to an embodiment of the present invention, an optical transmission method for transmitting a digital data signal and an analog broadcast signal by wavelength division multiplexing is presented. In this method, the analog broadcast signal is converted into an analog broadcast optical signal having a first wavelength. The digital data signal is randomized in a plurality of different modes, and each randomized data is output with identification information for restoration added. Among the plurality of randomized data, the data having the lowest possibility of interference with the analog broadcast signal is determined. According to the determination result, the randomized data with the identification information that is least likely to interfere with the analog broadcast signal is selected. The selected randomized data with identification information is converted into a digital data optical signal having a second wavelength different from the first wavelength. The analog broadcast optical signal and the digital data optical signal are multiplexed and output to the optical fiber transmission line. The optical signal of the first wavelength and the optical signal of the second wavelength are separated from the input light from the optical fiber transmission line. The separated signal light of the first wavelength is converted into a first electric signal. The separated signal light of the second wavelength is converted into a second electric signal. Then, the digital data signal is restored from the second electric signal.

  According to an embodiment of the present invention, there is provided an optical transmission system that includes an optical transmission device, an optical fiber transmission line, and an optical reception device, and transmits digital data signals and analog broadcast signals by wavelength division multiplexing. . The optical transmission device randomizes the first electric / optical converter that converts the analog broadcast signal into an analog broadcast optical signal of the first wavelength, and the digital data signal in a plurality of different modes, and each of the randomized data A data converter that adds identification information for restoration and outputs, and among the plurality of data randomized by the data converter, the data having the lowest possibility of interfering with the analog broadcast signal is determined A selector that selects one of a plurality of outputs of the data converter according to a determination result of the determination device and the determination device, and a digital data signal output from the selector are different from the first wavelength. A second electrical / optical converter for converting the digital data optical signal of the second wavelength, and an optical multiplexing device for multiplexing the output light of the first and second electrical / optical converters; Comprising the door. The optical receiver includes an optical separation device that separates the optical signal of the first wavelength and the optical signal of the second wavelength from the input light from the optical fiber transmission line, and the first optical signal separated by the optical separation device. A first photoelectric converter that converts signal light of one wavelength into an electrical signal; a second photoelectric converter that converts signal light of the second wavelength separated by the light separation device into an electrical signal; A data restoration circuit for restoring the digital data signal from the output electrical signal of the second photoelectric converter.

  An optical transmitter according to an embodiment of the present invention includes a first electric / optical converter that converts an analog broadcast signal into an analog broadcast optical signal having a first wavelength, and a digital data signal that is randomized in a plurality of different modes. A data converter that outputs each randomized data with identification information for restoration, and a plurality of data randomized by the data converter, the most likely to interfere with the analog broadcast signal A determination device for determining a low one, a selector for selecting one of a plurality of outputs of the data converter according to a determination result of the determination device, and a digital data signal output from the selector, A second electrical / optical converter for converting to a digital data optical signal having a second wavelength different from the first wavelength, and output light from the first and second electrical / optical converters Characterized by comprising an optical multiplexer for.

  According to the present invention, in an optical transmission system in which a digital data signal and an analog broadcast signal are transmitted by wavelength multiplexing using an optical fiber transmission line, a digital data signal caused by a nonlinear effect (mainly induced Raman effect) of the optical fiber. To reduce crosstalk from analog broadcast signals. Thereby, analog broadcast signals can be analog-transmitted with high quality.

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

  FIG. 1 shows a schematic block diagram of an embodiment of the present invention.

  The optical transmitter 10 includes an input terminal 12 for inputting an analog television signal and an input terminal 14 for inputting a digital data signal. The digital data signal is, for example, a 1.25 Gbps signal of Gigabit Ethernet. The electrical / optical converter 16 converts the analog television signal from the input terminal 12 into an analog television optical signal having the wavelength λ1.

  On the other hand, the block dividing circuit 18 blocks the digital data signal from the input terminal 14 every predetermined block length, for example, every 4095 bits, and supplies it to the randomizer 20 and 22. Each of the randomizers 20 and 22 randomizes the input data in units of bits according to different random number sequences in the block, and outputs the randomized data together with an identifier for restoring the original data.

  The output data of the randomizer 20 is applied to the fast Fourier transform circuit (FFT) 24 and the buffer 32, and the output data of the randomizer 22 is applied to the fast Fourier transform circuit (FFT) 26 and the buffer 34. The FFTs 24 and 26 perform fast Fourier transform on the output data of the randomizers 20 and 22, respectively, and supply the result to the switch control circuit 28. The outputs of the FFTs 24 and 26 indicate the spectra of the output data of the randomizers 20 and 22 in units of blocks.

  The block division circuit 18 and the randomizers 20 and 22 function as a data conversion circuit that converts an input digital data signal into a bit pattern that hardly interferes with an analog television signal.

  The switch control circuit 28 is a determination circuit that determines which of the outputs of the randomizers 20 and 22 is less likely to collide with the frequency component of the analog TV signal. For this determination, the analog TV signal input to the input terminal 12 is determined. The analog television signal frequency table 30 in which the frequency spectrum values are stored is referred to. Specifically, the switch control circuit 28 calculates and compares the sum of the frequency components included in the frequency range described in the analog television signal frequency table 30 based on the output data of the FFTs 24 and 26, and the randomizer 20, The switch 36 as a selector is controlled so as to select the smaller sum of the 22 outputs. The switch 36 is controlled by the switch control circuit 28 to select one of the outputs of the buffers 32 and 34. The buffers 32 and 34 are provided to compensate for delay due to processing in the FFTs 24 and 26 and the switch control circuit 28.

  Incidentally, the VHF channel frequencies in Japan are as follows, and the frequency information is stored in the table 30. That is, channel 1: 90-96 (MHz), channel 2: 96-102 (MHz), channel 3: 102-108 (MHz), channel 4: 170-176 (MHz), channel 5: 176-182 (MHz) ), Channel 6: 182-188 (MHz), channel 7: 188-194 (MHz), channel 8: 192-198 (MHz), channel 9: 198-204 (MHz), channel 10: 204-210 (MHz) ), Channel 11: 210-216 (MHz), and channel 12: 216-222 (MHz).

  The switch control circuit 28 compares the outputs of the FFTs 24 and 26 with the table 30 and determines which of the outputs of the randomizers 20 and 22 is less likely to collide with the frequency component of the analog television signal. The switch 36 is controlled in block units defined by Thereby, the switch 36 selects and outputs the data signal that is less likely to collide with the analog television signal on the frequency spectrum in units of blocks by the block dividing circuit 18. The electrical / optical converter 38 converts the output of the switch 36 into an optical signal having a wavelength λ2. The wavelength λ2 is different from the wavelength λ1.

  The optical multiplexing device 40 multiplexes the output signal light from the electrical / optical converters 16 and 38. The output light of the optical multiplexing device 40 is transmitted to the optical fiber transmission line 42.

  The optical signal propagated through the optical fiber transmission line 42 is incident on the optical separation device 52 of the optical receiver 50. The light separation device 52 separates the analog television light signal having the wavelength λ1 and the digital data signal light having the wavelength λ2, and supplies the former to the photoelectric converter 54 and the latter to the photoelectric converter 58.

  The photoelectric converter 54 converts the analog television signal light from the light separation device 52 into an electrical signal, that is, an analog television signal, and supplies it to the output terminal 56.

  The photoelectric converter 58 converts the digital data signal light from the light separation device 52 into an electrical signal and supplies the electrical signal to the binary discrimination circuit 60. The binary discrimination circuit 60 performs binary discrimination on the output electrical signal of the photoelectric converter 58 based on a predetermined threshold value, and supplies the discrimination result binary signal to the reverse randomizer 62. The reverse randomizer 62 restores the bit string randomized by the randomizer 20 or 22 according to the identifier added by the randomizer 20 or 22. The output data of the reverse randomizer 62 is output from the output terminal 64 to the outside. If there is no transmission error, the output data of the reverse randomizer 62 matches the digital data signal input to the input terminal 14.

  When it is necessary to correct a transmission error, as is well known, an error correction coding device may be connected to the preceding stage of the input terminal 14 and the error correcting device may be connected to the subsequent stage of the output terminal 64.

  In this way, in this embodiment, the data signal light and the analog television signal light are multiplexed after changing the bit arrangement of the digital data signal so as not to deteriorate the analog television signal transmitted by the analog light. Deterioration of the TV signal can be suppressed.

  FIG. 2 shows a schematic block diagram of an optical transmission device 10a having another configuration. The same components as those of the optical transmission device 10 shown in FIG. Operations different from those of the optical transmitter 10 will be described in detail.

  The optical transmission device 10 compares the spectral distributions of two randomized data signals, but the optical transmission device 10a measures the power intensity of the carrier frequency component of the analog television signal from the two randomized data signals, and is small. Select

  The low-pass filters (LPF) 110 and 112 are filters that pass the video signal frequency band of the analog television signal, and the 3 dB frequency is set to a frequency that is about 100 MHz higher than the maximum frequency used by the analog television signal. In this embodiment, since it is assumed that the maximum frequency of the analog TV signal is 222 MHz, the 3 dB frequency of the LPFs 110 and 112 is set to 322 MHz. The LPFs 110 and 112 transmit the frequency band of the analog television signal from the outputs of the randomizers 20 and 22, respectively, and the wattmeters 114 and 116 measure the power of the outputs of the LPFs 110 and 112, respectively. The switch control circuit 118 compares the measurement results of the power meters 114 and 116 and controls the switch 36 so as to select the smaller one.

  That is, when the measurement result of the wattmeter 114 is smaller than the measurement result of the wattmeter 116, the switch control circuit 118 causes the switch 36 to select the output of the buffer 32 in units of blocks, and vice versa. The output of the buffer 34 is selected in units of blocks. The buffers 32 and 34 are installed for the purpose of compensating the processing time in the LPFs 110 and 112, the power meters 114 and 116, and the switch control circuit 116. Accordingly, the buffers 32 and 34 can be omitted as long as the processing time in the LPFs 110 and 112, the wattmeters 114 and 116, and the switch control circuit 118 can be ignored.

  In this way, in this embodiment, the data signal randomized so as to reduce the influence on the analog television signal can be multiplexed and transmitted to the analog television signal with a simpler configuration than that of the first embodiment. Thereby, it is possible to reduce image quality deterioration due to crosstalk from a digital data signal to an analog television signal.

  FIG. 3 shows a schematic block diagram of an optical transmission apparatus 10b having still another configuration. The same components as those of the optical transmission device 10 shown in FIG. In this embodiment, in addition to the function of the optical transmission device 10, a randomizer 138 adapted to a specific bit string having a short code length, such as an idle code “10010001010011111010” having a code length of 20 bits defined by Ethernet (registered trademark); The selection means 132, 134, 136, 142 are added.

  The operation of the optical transmission device 10b different from the optical transmission device 10 will be described in detail. The block dividing circuit 130 blocks the digital data signal from the input terminal 14 every predetermined block length, for example, every 4095 bits, and supplies the blocked data to the switch 132 and the specific bit string counter 134. The specific bit string counter 134 counts a specific bit string in the blocked data. The specific bit string is, for example, an idle code having a code length of 20 bits defined by Ethernet (registered trademark). The counter 134 supplies the count result to the switch control circuit 136. The switch control circuit 136 connects the switches 132 and 142 to the contact A when the ratio of the specific bit string to the entire block is small, for example, 50% or less. Otherwise, the switches 132 and 142 are connected to the contact B.

  When the switch 132 is connected to the contact A, the output data of the contact A is processed by the randomizers 20 and 22, FFTs 24 and 26, the switch control circuit 28, the table 30, the buffers 32 and 34, and the switch 36 in the same manner as in the first embodiment. Is done.

  When the switch 132 is connected to the contact B, the output data of the contact B is input to the randomizer 138 adapted to the randomization of the specific bit string. The randomizer 138 generates a pseudo-random sequence so that the power distribution of the data after randomization becomes almost flat or has no large power in the frequency band of the analog TV signal when a specific bit string is repeatedly present in the block. Is preset. Similar to the randomizers 20 and 22, the randomizer 138 adds an identifier for restoration to the randomized data and outputs the data. The output of the randomizer 138 is supplied to the B contact of the switch 142 via the buffer 140. The data signal selected by the switch 142 is applied to the electrical / optical converter 38 and converted into an optical signal having a wavelength λ2.

  In this embodiment, the randomizer 138 randomizes the specific bit string counter 134, the switch control circuit 136, and the switches 132 and 142 when the specific bit string in the data divided by the block dividing circuit 130 exceeds a predetermined ratio. When data is transmitted and the specific bit string is less than the predetermined ratio, data randomized by the randomizer 20 or 22 is transmitted as in the first embodiment.

  Instead of the FFTs 24 and 26, the switch control circuit 28, and the analog television signal frequency table 30, LPFs 110 and 112, power meters 114 and 116, and a switch control circuit 118 may be employed as in the second embodiment.

  FIG. 4 shows a schematic block diagram of the randomizer 20, 22, 138. The pseudo-random sequence generator 150 generates a pseudo-random sequence bit pattern. The bit pattern of the pseudo random sequence generated by the pseudo random sequence generation device 150 is different for each randomizer 20, 22, and 138.

  The exclusive OR circuit 152 performs an exclusive OR operation between the output of the pseudo-random sequence generator 150 and the bit string from the switch 132 and outputs the result to the identifier adding device 154. The identifier adding device 154 adds an identifier for identifying the pseudo random sequence generated by the pseudo random sequence generating device 150 to the output data of the exclusive OR circuit 152. The output of the identifier adding device 154 becomes the output of the randomizer 20, 22, 138.

  FIG. 5 shows a schematic block diagram of the reverse randomizer 62 of the optical receiver 50 corresponding to the optical transmitter 10b. In order to correspond to the three randomizers 20, 22, and 138 of the optical transmission device 10b, the three pseudo random sequence generators 160, 162, and 164 are provided. For example, the pseudo random sequence generator 160 generates the same pseudo random sequence as the pseudo random sequence generator of the randomizer 20, and the pseudo random sequence generator 162 generates the same pseudo random sequence as the pseudo random sequence generator of the randomizer 22. The pseudo-random sequence generator 164 generates the same pseudo-random sequence as that of the randomizer 138.

  The identifier separating device 166 separates the identifier and the randomized data from the output data of the binary discriminating device 60 and supplies the former to the switch control circuit 168 and the latter to the exclusive OR circuit 172. Switch 170 is controlled by switch control circuit 168 to select one of the outputs of pseudo-random sequence generators 160, 162, 164. The switch control circuit 168 switches so as to select the output of the pseudo random sequence generator 160, 162 or 164 corresponding to the randomizer 20, 22 or 138 used in the optical transmitter 10b according to the identifier from the identifier separator 166. 170 is controlled.

  The pseudo random sequence selected by the switch 170 is applied to the exclusive OR circuit 172. The exclusive OR circuit 172 performs an exclusive OR operation between the pseudo random sequence from the switch 170 and the data string from the identifier separation device 166. By the exclusive OR circuit 172, the data randomized by the randomizer 20, 22 or 138 is restored.

  Although the randomizers 20, 22, 138 and the reverse randomizer 62 operating in units of 4095-bit length blocks have been described, a randomizer and reverse randomizer in byte units or other bit length units may be used instead. Also, devices that change the bit arrangement within a predetermined bit length, so-called interleaver and deinterleaver, may be used, which should be understood as the randomizer and reverse randomizer of the present invention, respectively.

  By setting the unit of block division to 4095 bits, the shortest color synchronization signal (2.51 μs) among the NTSC synchronization signals can be covered.

Each In randomizer 20, 22 and 138, for example, a pseudo-random sequence of code length 4095bit ^(PN2 12 -1), to use a this pseudo random sequence that shifted by one bit, and that the 2-bit shift.

  In the first, second, and third embodiments, the frequency component of the data signal that becomes an interference source in the analog television signal band is reduced in advance before transmission, and therefore, the analog television due to the nonlinear effect (mainly induced Raman effect) of the optical fiber. Signal quality degradation can be greatly reduced.

  In Example 3, even if the digital data signal includes a specific bit string having a short code length, for example, a repetition of an idle code consisting of 20 bits defined by Ethernet (registered trademark), the repetition of the specific bit string is performed. By randomizing so that a high power component does not appear at a specific frequency, image quality degradation of the analog television signal can be greatly reduced.

  Although the invention has been described with reference to specific illustrative embodiments, various modifications and alterations may be made to the above-described embodiments without departing from the scope of the invention as defined in the claims. This is obvious to an engineer in the field to which the present invention belongs, and such changes and modifications are also included in the technical scope of the present invention.

It is a schematic block diagram of the first embodiment of the present invention. It is a schematic block diagram of the optical transmission apparatus of another structure. It is a schematic block diagram of the optical transmission apparatus of another structure. It is a schematic block diagram of a randomizer. It is a schematic block diagram of a reverse randomizer.

Explanation of symbols

10, 10a, 10b: Optical transmitter 12: Input terminal 14: Input terminal 16: Electrical / optical converter 18: Block division circuit 20, 22: Randomizer 24, 26: Fast Fourier transform circuit (FFT)
28: Switch control circuit 30: Analog television signal frequency table 32, 34: Buffer 36: Switch 38: Electrical / optical converter 40: Optical multiplexer 42: Optical fiber transmission line 50: Optical receiver 52: Optical separator 54: Photoelectric converter 56: Output terminal 58: Photoelectric converter 60: Binary discrimination circuit 62: Reverse randomizer 64: Output terminals 110, 112: Low pass filter (LPF)
114, 1116: Power meter 118: Switch control circuit 130: Block division circuit 132: Switch 134: Specific bit string counter 136: Switch control circuit 138: Randomizer 140: Buffer 142: Switch 150: Pseudo random sequence generator 152: Exclusive OR Circuit 154: Identifier adding device 160, 162, 164: Pseudo random sequence generator 166: Identifier separating device 168: Switch control circuit 170: Switch 172: Exclusive OR circuit

Claims (17)

An optical transmission method for transmitting digital data signals and analog broadcast signals by wavelength division multiplexing,
(A) converting the analog broadcast signal into an analog broadcast optical signal having a first wavelength;
(B) randomizing the digital data signal in a plurality of different modes, and outputting each randomized data with identification information for restoration;
(C) Among the plurality of randomized data, determine the one that is least likely to interfere with the analog broadcast signal,
(D) According to the determination result of step (C), select the randomized data with the identification information that is least likely to interfere with the analog broadcast signal;
(E) converting the selected randomized data with the identification information into a digital data optical signal having a second wavelength different from the first wavelength;
(F) The analog broadcast optical signal and the digital data optical signal are multiplexed and output to an optical fiber transmission line;
(G) separating the optical signal of the first wavelength and the optical signal of the second wavelength from the input light from the optical fiber transmission line (42);
(H) converting the separated signal light of the first wavelength into a first electric signal;
(I) converting the separated signal light of the second wavelength into a second electrical signal;
(J) An optical transmission method which restores the digital data signal from the second electrical signal. The step (B)
The digital data signal is divided into blocks having a predetermined block length,
2. The method according to claim 1, further comprising the steps of: randomizing the data divided into the blocks in a plurality of different modes; and outputting each of the randomized data with identification information for restoration added thereto. The optical transmission method described. The step (J)
A binary discrimination of the second electrical signal;
The optical transmission method according to claim 1, further comprising each step of restoring a binary discrimination result based on the identification information. The step (C)
By the step (B), the frequency spectrum of each data randomized in a plurality of different modes is measured,
From each of the plurality of frequency spectrum measurement results and the frequency information of the analog broadcast signal, each step includes determining each of the plurality of randomized data having the lowest possibility of interference with the analog broadcast signal. The optical transmission method according to any one of claims 1 to 3, wherein: The step (C)
Extracting frequency components that interfere with the analog broadcast signal from each data randomized in a plurality of different modes by the step (B),
Measure the power of each extracted frequency component,
The method includes the steps of determining, from a comparison of power measurement results, a plurality of data randomized by the step (B) and having the lowest possibility of interference with the analog broadcast signal. Item 4. The optical transmission method according to any one of Items 1 to 3. Furthermore,
Count the number of specific bit strings included in the digital data signal,
The digital data signal includes each step of selecting data randomized by a specific randomizer (138) regardless of the determination result of step (C) when a specific bit string is included in a predetermined ratio or more. The optical transmission method according to claim 1. An optical transmission system comprising an optical transmitter (10), an optical fiber transmission line (42), and an optical receiver (50), and transmitting a digital data signal and an analog broadcast signal by wavelength division multiplexing.
The optical transmitter (10, 10a, 10b)
A first electrical / optical converter (16) for converting the analog broadcast signal into an analog broadcast optical signal of a first wavelength;
A data converter (18, 20, 22) for randomizing the digital data signal in a plurality of different modes and outputting each of the randomized data with identification information for restoration;
A determination device (24, 26, 28, 30; 110, 112, 114, 116, which determines the lowest possibility of interfering with the analog broadcast signal among the plurality of data randomized by the data converter. 118)
A selector (36) for selecting one of a plurality of outputs of the data converter according to the determination result of the determination device;
A second electrical / optical converter (38) for converting the digital data signal output from the selector into a digital data optical signal having a second wavelength different from the first wavelength;
Optical multiplexer (40) for multiplexing the output light of the first and second electric / optical converters (16, 38)
And
The optical receiver (50) is
An optical separation device (52) for separating the optical signal of the first wavelength and the optical signal of the second wavelength from the input light from the optical fiber transmission line (42);
A first photoelectric converter (54) for converting the signal light of the first wavelength separated by the light separation device (52) into an electric signal;
A second photoelectric converter (58) for converting the signal light of the second wavelength separated by the light separation device (52) into an electric signal;
Data restoration circuit (60, 62) for restoring the digital data signal from the output electrical signal of the second photoelectric converter (58)
An optical transmission system comprising: The data converter
A block dividing circuit (18) for dividing the digital data signal into blocks having a predetermined block length;
A plurality of randomizers (20, 22) for randomizing the output data of the block dividing circuit (18) in a plurality of different modes and adding the identification information for restoration to each of the randomized data.
The optical transmission system according to claim 7, further comprising: The data restoration circuit is
A binary discrimination circuit (60) for binary discrimination of the output electrical signal of the second photoelectric converter (58);
A restoration circuit (62) for restoring the digital data signal from the output of the binary discrimination circuit (60) by the identification information
The optical transmission system according to claim 7, further comprising: The determination device is
A plurality of frequency spectrum measuring devices (24, 26) for measuring the frequency spectrum of each data randomized in a plurality of different modes by the data converter;
A frequency table (30) for storing frequency information of the analog broadcast signal;
From the respective measurement results of the plurality of frequency spectrum measuring devices (24, 26) and the frequency table, among the plurality of data randomized by the data converter, there is the lowest possibility of interference with the analog broadcast signal. Equipment for determining things (28)
The optical transmission system according to claim 7, further comprising: The determination device is
A plurality of filters (110, 112) for extracting frequency components that interfere with the analog broadcast signal from each data randomized in a plurality of different modes by the data converter;
A plurality of wattmeters (114, 116) for measuring the power of each output of the plurality of filters;
By comparing the measurement results of the plurality of wattmeters (114, 116), it is determined which of the plurality of data randomized by the data converter has the lowest possibility of interference with the analog broadcast signal. (118) to do
The optical transmission system according to claim 7, further comprising: One of the plurality of randomizers is a specific randomizer (138) suitable when the digital data signal includes a specific bit string at a predetermined ratio or more,
The optical transmitter (10b) further includes
A specific bit string counter (134) for counting the number of the specific bit strings included in the output of the block dividing circuit;
Means (132, 136, 142) for selecting the specific randomizer (138) when the digital data signal includes a specific bit string in a predetermined ratio or more according to the count result of the specific bit string counter (134).
The optical transmission system according to claim 8, further comprising: A first electrical / optical converter (16) for converting an analog broadcast signal into an analog broadcast optical signal of a first wavelength;
A data converter (18, 20, 22) for randomizing the digital data signal in a plurality of different modes and outputting each of the randomized data with identification information for restoration;
A determination device (24, 26, 28, 30; 110, 112, 114, 116, which determines the lowest possibility of interfering with the analog broadcast signal among the plurality of data randomized by the data converter. 118)
A selector (36) for selecting one of a plurality of outputs of the data converter according to the determination result of the determination device;
A second electrical / optical converter (38) for converting the digital data signal output from the selector into a digital data optical signal having a second wavelength different from the first wavelength;
Optical multiplexer (40) for multiplexing the output light of the first and second electric / optical converters (16, 38)
An optical transmitter characterized by comprising: The data converter is
A block dividing circuit (18) for dividing the digital data signal into blocks having a predetermined block length;
A plurality of randomizers (20, 22) for randomizing the output data of the block dividing circuit (18) in a plurality of different modes and adding the identification information for restoration to each of the randomized data.
The optical transmission device according to claim 13, further comprising: The determination device is
A plurality of frequency spectrum measuring devices (24, 26) for measuring the frequency spectrum of each data randomized in a plurality of different modes by the data converter;
A frequency table (30) for storing frequency information of the analog broadcast signal;
From the respective measurement results of the plurality of frequency spectrum measuring devices (24, 26) and the frequency table, among the plurality of data randomized by the data converter, there is the lowest possibility of interference with the analog broadcast signal. Equipment for determining things (28)
The optical transmission device according to claim 13 or 14, further comprising: The determination device is
A plurality of filters (110, 112) for extracting frequency components that interfere with the analog broadcast signal from each data randomized in a plurality of different modes by the data converter;
A plurality of wattmeters (114, 116) for measuring the power of each output of the plurality of filters;
By comparing the measurement results of the plurality of wattmeters (114, 116), it is determined which of the plurality of data randomized by the data converter has the lowest possibility of interference with the analog broadcast signal. (118) to do
The optical transmission device according to claim 13 or 14, further comprising: One of the plurality of randomizers is a specific randomizer (138) suitable when the digital data signal includes a specific bit string at a predetermined ratio or more,
The optical transmitter further includes
A specific bit string counter (134) for counting the number of the specific bit strings included in the output of the block dividing circuit;
Means (132, 136, 142) for selecting the specific randomizer (138) when the digital data signal includes a specific bit string in a predetermined ratio or more according to the count result of the specific bit string counter (134).
The optical transmission device according to claim 13, further comprising:

Images