JPS63284956A - Optical transmission system - Google Patents

Abstract

PURPOSE:To make the rise of a transmission clock frequency unnecessary as satisfying a BSI condition, by setting an information system string as two series of AMI encoded strings, and replacing a part where a 0 signal of prescribed bits continues by a specific pattern, then, transmitting it. CONSTITUTION:At a transmitter 12, the information system string inputted from a terminal 17 is delayed at an 8 bit delay circuit 19, and is inputted to an OR gate 25 by taking synchronization with a transmission clock from a terminal 18. Also, the information system string is inputted to a shift register 20, and the decision of the 0 signal is applied on all of the eight bits at a detection circuit 21, and when it is decided that all eight bits are 0 signals, the information system string, after the specific pattern being inserted from a pattern generation circuit 22 to the register 20, is sent to a gate 25. The gate 25 takes the logical sum of both inputs, and outputs a result to gate circuits 29 and 30. The AMI (alternate mark inversion) code outputs of the gate circuits 29 and 30 are sent to light emitting elements 31 and 32, and after being converted to optical signals with wavelength lambda1 and lambda2, are sent to an optical fiber 33.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical transmission system using an optical transmission line, and particularly to a transmission line encoding system.

[Conventional technology] In optical transmission systems that transmit digital information using light,
In order to obtain good transmission quality, bit sequence independence (B
It Sequence Independence
(hereinafter referred to as BSI) conditions must be met.

Figure 4 shows, for example, Research and Practical Application Report Volume 28 No. 9 (19
"r32Mb/s and 100Mb/S digital optical cable transmission systems" published on pages 2I to 46 of Nippon Telegraph and Telephone Public Corporation in 1979, and Research and Practical Application Report, Vol. 32, No. 3.
A time chart showing such a conventional optical transmission system as shown in "Design and Characteristics of IP-400M Terminal Station Relay Equipment" published on pages 23 to 34 of the issue (published by Nippon Telegraph and Telephone Public Corporation in 1983). In the figure, I is the bit number,
2 is the information series to be transmitted, 3 is the coded mark inversion (Coded M a
rkI nvrsion (hereinafter referred to as CMI) encoding system; 4 is the code sequence encoded using the information sequence 2,
m Binary with l Complete
m=
This is a code sequence encoded using an encoding method for IQ (hereinafter referred to as 10BIc encoding method).

Next, the operation will be explained. The code sequence based on the CMI encoding method is based on the transmission path [knock frequency is twice the frequency of information sequence 2 to be transmitted, an “OI” pattern is assigned to the “0” signal of the information sequence 2, "00° pattern or "It" pattern is assigned to the "00° pattern" or "It" pattern, and each time the "l" signal occurs in information series 2, the pattern is changed from 00° to "11" or "°11".
By alternately reversing the pattern from “00” to “00”
゛When the number of consecutive signals is 3 or less and the mark rate is 1/2, B
Encoding is performed that satisfies the S1 condition.

Furthermore, code sequence 4 based on the l0BIC encoding method is (1
By performing speed conversion of 0+1)/10, l redundant bits are secured for every 10 bits, the 1st to 10th bits of the information sequence 2 to be transmitted are placed in the 1st to 10th bits, and the 11th bit is The information sequence 2 is added to the redundant bit of the bit.
In the illustrated example, the shaded 11th bit is inserted with the complementary code of the 8th bit "O".
A "BI" signal obtained by inverting the "0" signal is loaded as a complementary code. This makes it possible to suppress the worst consecutive number of "0" signals to within 10+1, and performs encoding that satisfies the BSI conditions.

[Interlayer points to be solved by the invention] Since the conventional optical transmission system is configured as described above,
The CMI encoding method not only doubles the transmission line clock frequency, but also requires a transmission band that is twice the information transmission speed.
In the 0BIG encoding method, for the information sequence to be transmitted (
Since the transmission line clock frequency is 10+,1)/lO times higher, speed conversion with the clock source is required, resulting in a problem that the device becomes complicated.

This invention was made to solve the above-mentioned problems, and is a BSI system that does not increase the transmission line clock frequency, does not require speed conversion, and allows easy reception timing recovery.
The purpose is to obtain an optical transmission system that satisfies the conditions.

[Means for solving the problem] The optical transmission system according to the present invention
Extract every other l” signal, and extract “0” from a predetermined number of bits or more.
A first optical signal sequence generated by replacing the continuous portion of the signal with a specific pattern, and the remaining “l°” signal of the information sequence are extracted, and the continuous portion of the “0” signal is replaced with the specific pattern. The second optical signal sequence generated by the optical transmission line is transmitted to the optical transmission line, and the information sequence sent from the first and second optical signal sequences received from the optical transmission line is reproduced.

[Operation] The optical transmission system of the present invention generates two optical signal sequences for the information sequence to be transmitted, and uses each as an alternate mark inversion (AI) of the information sequence.
As a code string of different polarity in a code string based on a coding method (hereinafter referred to as AMI), a portion where "0° signals are continuous for a predetermined number of bits or more in the optical signal series of both systems includes an "I" signal. By replacing it with a specific pattern, an optical transmission system can be realized that does not require speed conversion, does not increase the transmission line clock cycle frequency, and does not satisfy the BS1 condition.

``Example'' An example of the present invention will be described below with reference to the drawings. 1st
In the figure, l is a bit number and 2 is an information sequence to be transmitted, which are the same as those in the conventional system, which are given the same reference numerals in FIG. 5 is the transmission clock, 6 is the information series 2
7 is the second code conversion sequence generated for the information sequence 2;
The code conversion sequence 6 converts, for example, the positive side of the code sequence of the information sequence 2 to be transmitted according to the AMI encoding system, in which a continuous portion of the "θ' multiplied signal has a predetermined number of bits or more, for example, 8 bits or more, into 8 bits. The second code conversion sequence 7 is a signal with a specific pattern of 8 bits, for example, “10011001”, in which 8 bits or more of consecutive “0” signals are present on one side of the code string based on the AMI encoding method. A specific pattern of signal “10011001” is generated in 8-bit units.
8 is the first code conversion sequence 6
9 is a first optical signal sequence that emits light in accordance with the above-mentioned second code conversion sequence.

Further, lO is a received code sequence generated based on the first optical signal sequence 8, If is a received code sequence generated based on the second optical signal sequence 9, and 12 is a received code sequence I
A synthetic timing component synthesized from O and 11, 13 a reproduction timing reproduced based on this synthetic timing component 12, 14 a synthetic data sequence synthesized from the received code sequence lO and 11, and 15 a synthetic data sequence. 14
This is a reproduction code sequence that is reproduced based on .

FIG. 2 is a block diagram showing an example of a transmitting device. In the figure, 16 is a transmitting device, 17 is a terminal to which the information series 2 to be transmitted is manually input, and 18 is a terminal to which the transmitting clock 5 is input. Terminal! 9 is a delay circuit that delays the information series 2 input from the terminal 17 by 8 bits, 20 is an 8-bit shift register, and 21 is this shift register 20.
A detection circuit 22 detects that all the signals in the shift register 2I become "0", and a detection circuit 22 detects a specific pattern of signals "1001" inserted into the shift register 20 in response to the output of the detection circuit 2I.
23 is a gate circuit that ANDs the output of the delay circuit 19 and the transmission clock 5; 24 is a gate circuit that ANDs the output of the shift register 20 and the transmission clock; 25 is an OR gate that calculates the logical sum of the outputs of the gate circuits 23 and 24, 2
6 is a flip-flop whose state is inverted every time the output of the gate circuit 23 arrives; 27.28 is this flip-flop;
29 is a gate circuit that takes the AND of the two outputs of the 0-tube 26 and the output of the delay circuit 19; 29 is a gate circuit that takes the AND of the output of the OR gate 25 and the output of the gate circuit 27;
30 is a gate circuit that takes the logical product of the output of the OR gate 25 and the output of the gate circuit 28; 31 is a gate circuit that emits light with a wavelength λ; and is activated by the output of the gate circuit 29 to generate the first optical signal sequence 8. The light emitting element 32 emits light of wavelength λ,
A light-emitting element 33 is activated by the output of the gate circuit 30 to generate the second optical signal sequence 9, and 33 represents each of these light-emitting elements 31 and 32.
This is an optical fiber serving as an optical transmission line that couples the first optical signal sequence 8 and the second optical signal sequence 9 to the optical signal sequence.

Further, FIG. 3 is a block diagram showing an example of a receiving device, and in the figure, 34 is a receiving device, 35 is coupled to the optical fiber 20 and is sensitive only to light of wavelength λ1, and the first
A light receiving element 36 that receives the optical signal sequence 8 is also coupled to the optical fiber 33 and is sensitive only to light of wavelength λ,
A light-receiving element 37 receives the second optical signal sequence 9; 37 is a regenerative receiving unit that generates a received code sequence lO corresponding to the first optical signal sequence 8 from the output of the light-receiving element 35; A regenerative receiving unit 39 reproduces the received code sequence 11 corresponding to the second optical signal sequence 9 from the output of the element 36, and a reproducing receiving unit 39 reproduces the received code sequence 10. 40 is a timing reproducing unit that synthesizes a composite timing component I2 based on the composite timing component I2 and reproduces a reproduction timing 13 from the synthesized composite timing component 12, and 40 is an exclusive of the received code sequences IO and 1 outputted by both the reproduction receiving units 37 and 38. 41 is an inverting circuit that inverts the polarity of the composite data series 14 outputted from the exclusive OR circuit 40; 42 is the exclusive OR circuit 42; A flip-flop that reproduces the reproduced code sequence 15 based on the outputs of the circuit 40, the inverting circuit 41, and the timing reproducing unit 39; 43 is the reproduced code sequence 1;
5, and 44 is a terminal that outputs the reproduction timing 13.

Next, the operation will be explained. In the transmitting device 12, terminal 1
3, the information series 2 to be sent manually is sent to the delay circuit 19.
Terminal 1 is delayed by 8 bits at gate circuit 23.
The clock signal 8 is input to the OR gate 25 in synchronization with the manually inputted transmission clock 5 . Further, the information series 2 is also input to the shift register 20, and the detection circuit 21 determines whether all 8 bits in the shift register 20 are '0' signals. When it is detected that all the bits are "0# signals", the pattern generation circuit 22 is activated, and the signal of the specific pattern "10011001" generated by the pattern generation circuit 22 is inserted into the shift register 20. The output of this shift register 20 is also synchronized with the transmission clock by the gate circuit 24 and then inputted to the OR gate 25 . OR gate 25 takes the logical sum of these two inputs and outputs the result to gate circuits 29 and 30. The output of the gate circuit 32 is also input to the flip-flop 26, and therefore, the flip-flop 26 inverts its state every time the signal of the information series 2 to be transmitted becomes "1". The two outputs of this flip-flop 26 are connected to gate circuits 27 and 27, respectively.
．． 28 and the information sequence 2 delayed by the delay circuit 19 is ANDed to generate gate pulses for the gate circuits 29 and 30. The gate circuits 29 and 30 gate the output from the OR gate 25 according to this gate pulse, and the gate circuit 29 extracts the odd-numbered "l" signal of the information series 2 to be transmitted, and extracts the code string based on the AMI encoding method. A first code conversion in which a part of a one-polarity code string in which 8 or more consecutive "0" signals are present is replaced in units of 8 bits with a signal of a specific pattern "10011001" generated by the pattern generation circuit 22. The gate circuit 30 also transmits the even-numbered "1" of the information series 2 to be transmitted.
“In the code string of the other polarity of the code string according to the AMI encoding method from which the signal was extracted, the part where 8 bits or more of consecutive “0” signals are detected is a specific pattern generated by the pattern generation circuit 22 in units of 8 bits. A second code conversion sequence 7 is generated in which the signal is replaced with the signal "10011001".The output of this gate circuit 29 is sent to the light emitting element 31,
emits light of wavelength λ1 in response to the output of this gate circuit 29, and generates the first optical signal sequence 8. Similarly, the output of the gate circuit 30 is also sent to the light emitting element 32.
1 also responds to the output of the gate circuit 30 to change the wavelength λ.

The second optical signal sequence 9 is generated by emitting light.

These first and second optical signal sequences 8 and 9 are transmitted to the light emitting element 31
．． The signal is sent to a receiver 34 via an optical fiber 33 coupled to a receiver 32 .

The first and second optical signal sequences 8.9 transmitted through the optical fiber 33 to the receiving device 34 are input to the light receiving elements 35 and 36. The light-receiving element 35 receives the first optical signal sequence 8 by sensing only the light with the wavelength λ1, and the light-receiving element 36 receives the first optical signal sequence 8 with the wavelength λ1.
, and receives the second optical signal sequence 9.

The output of the light-receiving element 35 is sent to a reproducing receiver 37, and the output of the light-receiving element 36 is sent to a reproducing receiver 38, where they are regenerated as received code sequences lO and it, respectively, and input to a timing reproducing circuit 39. Timing regeneration circuit 26
Then, a composite timing component 12 is synthesized from these received code sequences 10 and 11, and a reproduction timing 13 is reproduced by driving a tank circuit or a PLL circuit using this composite timing component 12, and outputted from a terminal 44. This received code sequence 10.11 is the exclusive OR circuit 4
0 is also input, and a specific pattern signal in which both received code sequences IO and 11 are "l" signals is combined into a composite data sequence 14 from which signals of a specific pattern are removed.

This composite data series 14 outputted from the exclusive OR circuit 40 is directly inputted to a flip-flop 42 via an inverting circuit 41, and the flip-flop 42 inputs both inputs and the reproduction timing outputted from the timing reproducing section 39. A reproduced code sequence 15 is reproduced based on 13 and outputted from a terminal 44.

In the above embodiment, the case where there is one optical transmission line has been explained, but it is also possible to prepare two optical transmission lines and transmit the first optical signal series and the second optical signal series through different optical transmission lines. In that case, it is also possible to use light of the same wavelength for the first optical signal series and the second optical signal series.

[Effects of the Invention] As described above, according to the present invention, two optical signal sequences are generated for an information sequence to be transmitted, and each is encoded with a different polarity of a code sequence based on the AMI encoding method of the information sequence. As a code string, parts where these "0" signals continue for a predetermined bit or more are replaced with a specific pattern, so there is no need for speed conversion, there is no need to increase the transmission line clock frequency, and it is possible to recover the reception timing. easy BS
This has the effect of realizing an optical transmission system that satisfies one condition.

[Brief explanation of drawings]

FIG. 1 is a time chart showing an optical transmission system according to an embodiment of the present invention, FIG. 2 is a block diagram showing its transmitting device, FIG. 3 is a block diagram showing its receiving device, and FIG. 4 is a conventional optical transmission system. It is a time chart showing a transmission method. 2 is an information sequence to be transmitted, 8 is a first optical signal sequence, 9 is a second optical signal sequence, 10.11 is a received code sequence, 12 is a reproduction timing, 13 is a reproduction code sequence, 16 is a transmitter, 33 is an optical transmission line (optical fiber), and 34 is a receiving device. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Figure 1 Figure 2 Figure 3

Claims (5)

[Claims] (1) In an optical transmission system in which a transmitting device and a receiving device are connected by an optical transmission path and an information sequence based on an optical signal is transmitted onto the optical transmission path, the transmitting device transmits “1” of the information sequence.
Extract every other signal, and extract a portion of the information sequence in which "0" signals are consecutive for a predetermined number of bits or more into a signal of a specific pattern of the predetermined number of bits including a "1" signal for each of the predetermined number of bits. The first optical signal sequence generated by replacing with A second optical signal sequence generated by replacing the information with the optical transmission line is sent to the optical transmission line, and the receiving device reproduces the information sequence from the first and second optical signal sequences received from the optical transmission line. An optical transmission method characterized by: (2) The receiving device reproduces a received code sequence for each system from the first and second optical signal sequences, synthesizes the received code sequences of the respective systems, and determines the reproduction timing and 2. The optical transmission system according to claim 1, wherein a reproduced code sequence is generated. (3) Use lights of different wavelengths as the light of the first optical signal series and the light of the second optical signal series, and transmit the first and second optical signal series on the same optical transmission path. Claim 1 or 2, characterized in that
Optical transmission method described in section. (4) Optical transmission according to claim 1 or 2, characterized in that the first optical signal series and the second optical signal series are transmitted on separate optical transmission paths. method. (5) The optical transmission system according to claim 4, characterized in that the light of the first optical signal series and the light of the second optical signal series have the same wavelength.