JP2008312138A - Optical transmission method, encoding method, optical transmission system, and optical transmission device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical transmission system which includes both a parallel transmission system and a multilevel transmission system, with its transmission capacity being increased in the parallel transmission system, independently of the multilevel transmission system. <P>SOLUTION: The optical transmission system includes a first optical reception device 20B, capable of discriminating the intensities of a plurality of optical signals which differ in the wavelength for each wavelength of the optical signal transmitted from an optical transmitting device 10 and a second optical receiving device 20A, which collectively discriminate a plurality of wavelengths. The optical transmission device 10 transmits encoded information, discriminated by the second optical receiving device 10B, such that the sum of optically received intensities is the same and is also discriminated by the first optical reception device 20A, such that the combination of wavelength is different. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to high-speed optical communication, and particularly when a plurality of transmission methods are mixed on the same transmission medium, an optical transmission method, an encoding method, an optical transmission system, and an optical transmission method that increase the transmission capacity economically. The present invention relates to an optical transmitter.

  Passive optical networks (PON) are widely used as leading optical fiber access technologies. The PON is a star network that connects one optical subscriber line intra-station equipment (OLT) and a plurality of optical subscriber line residential equipment (ONU) through an optical power splitter that is a passive element. A one-core optical fiber is connected to the OLT, and this optical fiber is branched into a plurality of optical fibers via an optical power splitter and connected to the ONU. Since this PON shares the OLT, the optical power splitter, and the optical fiber between them with a plurality of users, it can provide a low-cost service.

  As a technique for increasing the transmission capacity of a PON, there is a parallel transmission system (FIG. 9) in which optical signals having different wavelengths are wavelength-multiplexed on the same medium and the transmission capacity is increased in parallel by the number of wavelengths. In the downstream signal of the parallel transmission system, the optical transmission device 10 (OLT) converts a high-speed binary electric signal into a plurality of low-speed binary optical signals by the S / P converter 14, and the plurality of low-speed two-way optical signals. The value optical signal is generated into a plurality of optical signals having different wavelengths by the plurality of optical transmitters 11, multiplexed by the wavelength multiplexer 12, and transmitted into the optical fiber transmission line 40. In the optical receiver 20B (ONU) that receives the optical signal via the optical power splitter 40, the wavelength demultiplexer 22 decomposes the optical signal into a plurality of optical signals, and uses the plurality of optical receivers 23 to generate a plurality of optical signals. The signal is converted into a low-speed binary electric signal, and is converted into one high-speed binary optical signal by the P / S converter 24. In this parallel transmission method, the transmission capacity increases by the number of multiplexed wavelengths. However, the optical transmitter 10 requires an expensive wavelength multiplexer 12 or the optical receiver 23 of the optical receiver 20 has the number of wavelengths. However, there is a problem in economic efficiency.

  On the other hand, intensity modulation type multi-value transmission systems (Patent Documents 1 and 2) have been proposed as methods for increasing the transmission capacity using a modulation method. In the multi-value transmission method, an expensive optical filter is not required in the ONU, and reception is possible with a single receiver. Therefore, an economical increase in transmission capacity is expected. For example, in the configuration example of Patent Document 1, When optical signals from independent light sources are multiplexed, phase control of each light source is practically impossible, resulting in interference noise. Therefore, it is difficult to transmit information substantially. Further, in the configuration example of Patent Document 2, the required external modulator becomes large in accordance with the multi-valued number of optical signals. Since the external modulator is relatively expensive, it cannot be said that the method is suitable for economy.

  With the spread of the Internet in the future, the demand for higher-speed communication services will increase, and the demand for services with relatively low speed and low usage fees will also increase. On the other hand, there is a request from the service provider side to suppress an increase in equipment cost due to service diversification. In order to meet both of these requirements, a method of sharing the optical fiber transmission line and the station side transmission apparatus by a plurality of transmission methods is conceivable.

  As a communication method that solves the problems of the conventional intensity modulation type multi-value transmission system and achieves economy by the above method, optical signals of multiple wavelengths having the same intensity are received in a batch by a single optical receiver. A multi-value transmission scheme (FIG. 10) that increases the transmission capacity by identifying as a multi-value code has been proposed.

  In the downstream signal of this multilevel transmission system, the optical transmission device 10 (OLT) converts a high-speed binary electrical signal into a multilevel logic signal by the multilevel logic conversion unit 13, and converts the multilevel code into a binary value. Are converted into parallel signals, a plurality of optical signals having different wavelengths are generated by the plurality of optical transmitters 11, combined by the wavelength multiplexer 12, and transmitted into the optical fiber transmission line 40. In the optical receiver 20A (ONU) that has received the optical signal via the optical power splitter 40, the optical receiver 21 collectively receives the optical signal, and the multilevel binary converter 26 converts it into a binary signal.

  Considering a mixed downlink transmission method with the parallel transmission method using this multi-value transmission method, the parallel transmission method and the multi-value transmission method are common in that a plurality of light sources are provided in the OLT. It is possible to share the OLT by using the devices in a time-sharing manner. In addition, when applying these two methods to the PON, different information can be transmitted for each user by applying the time division multiplexing method in each of the parallel transmission method and the multi-value transmission method. it can.

In addition, when comparing these two methods, the increase in the transmission capacity of the multi-value transmission system shows a logarithmic increase with respect to the addition of the wavelength, so the increase rate of the transmission capacity may be lower than that of the parallel transmission system. I understand. In short, the parallel transmission method is fast and expensive, and the multilevel transmission method is not as high as the parallel transmission method, but can provide a high-speed and economical service.
JP 63-005633 A JP 2003-258733 A

  As described above, when a high-speed and expensive parallel transmission method and a reasonably high-speed and low-cost multi-value transmission method coexist on one optical fiber transmission line and used by time division multiplexing, a plurality of services are used in the same optical fiber. There is a merit that it can be provided by a transmission line and the same OLT, but such mixed accommodation has the following problems.

  For example, when a user who uses a multi-value transmission service requests a higher-speed service, the user can change the service to a parallel transmission service, but a user who uses a parallel transmission service When a faster service is sought, it is difficult to increase the speed of only the parallel transmission system without affecting the user equipment of the multilevel transmission system. That is, there is a demerit that it is difficult to independently upgrade each method due to mixed accommodation.

  An object of the present invention is to receive light without identifying wavelengths when a system for identifying and receiving wavelengths (parallel transmission system) and a system for simultaneous reception without identification (multi-level transmission system) are mixed. By transmitting wavelength information that is not multi-level identified to the apparatus from the optical transmitter, only the method of identifying and receiving the wavelength can be independently increased in transmission capacity.

In order to achieve the above object, the invention according to claim 1 multiplexes and transmits a plurality of optical signals having different wavelengths that are intensity-modulated and synchronized, and branches the combined optical signal. A plurality of optical receivers, wherein the plurality of optical receivers are configured such that the intensities of the optical signals having different wavelengths are wavelengths of optical signals transmitted from the optical transmitter or One or more first optical receivers that can be identified for each wavelength and one or more second optical receivers that collectively identify a plurality of wavelengths are mixed, and from the optical transmitter, the second optical receiver The optical receiving apparatus transmits encoded information that is identified as having the same total received light intensity and that identifies a difference in wavelength combination in the first optical receiving apparatus.
The invention according to claim 2 is an encoding method used in the optical transmission method according to claim 1, wherein an optical signal of n waves having different wavelengths (n is an integer satisfying n ≧ 3) is transmitted from the optical transmitter. When transmitting, a specific m-wave optical signal (m is an integer satisfying 2 ≦ m ≦ n−1) among the n-wave optical signals having different wavelengths can be taken by the second optical receiver. Within the range identified as n + 1−m received light intensity from adjacent k (k is an integer satisfying 1 ≦ k ≦ m−1) to k + n−m among n + 1 received light intensity from 0 to n. Independently of the n + 1−m received light intensity that can be obtained by the second optical receiver, any i (i is an integer satisfying i = k) wave among the m-wave optical signals is turned on, and the remaining A set of ON / OFF states of the n-wave optical signal so that the mi wave can be set to OFF. Controls were, the second can not be identified by the optical receiver, the first combination of _m C _i values of ON / OFF states of the _m C _i Street the particular m wave can take the optical receiver It is transmitted as encoded information that can be identified as a multi-level code.
According to a third aspect of the present invention, in the optical transmission method according to the first aspect, the optical signal transmission time to the first optical receiving device and the optical signal transmission time to the second optical receiving device are divided. In the allocation time to the first optical receiver, a signal is transmitted so as to convey information to the first optical receiver, and in the allocation time to the second optical receiver, the first A signal received as a multi-level code for the second optical receiver and received as the encoded information is transmitted to the first optical receiver.
According to a fourth aspect of the present invention, in the optical transmission method according to the third aspect, when a plurality of the first optical receivers are connected, encoded information that can be identified by the first optical receiver. Is transmitted to only a part of the first optical receiver.
The invention according to claim 5 is the optical transmission method according to claim 3, wherein the encoded information is encoded information using the encoding method according to claim 2.
The invention according to claim 6 converts a high-speed binary electric signal into a plurality of low-speed binary optical signals having different wavelengths, and multiplexes and transmits the plurality of binary optical signals to one optical transmission medium. And a function of transmitting encoded information in which the combination of wavelengths is controlled within a range in which the sum of received light intensity received by the optical receiver is identified as the same.
The invention according to claim 7 is the optical transmission apparatus according to claim 6, wherein the encoded information is information created by the encoding method according to claim 2.
The invention according to claim 8 includes one or more first optical receivers that demultiplex a received signal and identify each wavelength using an optical receiver, and a single optical receiver for signals for a plurality of wavelengths. One or two or more second optical receivers that are collectively received and identified as a multilevel code, and convert a high-speed binary electric signal into a plurality of low-speed binary optical signals having different wavelengths, and the plurality of low-speed optical signals A function of combining and transmitting a binary optical signal to one optical transmission medium, and controlling a combination of wavelengths in a range in which the total sum of received light intensity is identified as the same in the second optical receiver, And an optical transmitter having a function of transmitting encoded information that can be identified only to the first optical receiver.
The invention according to claim 9 is an optical transmission system using the optical transmission method according to claim 3, wherein the first optical receiver according to claim 8 and the second optical receiver according to claim 8 are provided. An optical receiver comprising the optical receiver according to claim 8, wherein the second optical transmitter discards a signal received at a time other than each allocated time, and the first optical receiver Has a function of identifying the encoded information within a time allotted to the second optical receiver, and the optical transmitter transmits the high-speed binary electric signal to a plurality of low-speed 2 signals having different wavelengths. When converting to a value optical signal, the optical signal transmission time to the first optical receiver is converted to a low-speed binary optical signal that can be identified for each wavelength, The signal transmission time is determined so that the signal can be identified as a multi-level code when collectively identified. And having a function of converting a plurality of low-speed binary optical signal becomes.
The invention according to claim 10 is an optical transmission system using the optical transmission method according to claim 4, wherein the first optical receiver according to claim 9 and the second optical receiver according to claim 9 are provided. An optical receiver comprising the optical receiver according to claim 9, wherein the first optical receiver has a function of identifying and receiving only the information addressed to itself by identifying the destination of the encoded information And the optical transmitter has a function of transmitting destination information added to encoded information that can be identified by the first optical receiver.

  According to the present invention, wavelength information that is not used in the multilevel transmission system is effectively used, so that the transmission capacity of the parallel transmission system can be increased independently without affecting the multilevel transmission system. .

<First embodiment>
FIG. 1 shows an optical transmission system according to a first embodiment of the present invention. The optical transmitting apparatus 10 converts a binary input signal into a multi-level logic code, and binary parallel so that the multi-level code can be received as a multi-level code when received by the collective receiver of the optical receiving apparatus 20A. A plurality of binary signals, which are converted into a code (mark rate of each channel is ½) and synchronized with _n optical transmitters 11 _{1 to} 11 _n (n is an integer of 3 or more) having different wavelengths. Generated, multiplexed by the optical multiplexer 12, and transmitted. The optical transmitter 10 is connected to an optical fiber transmission line (medium network) 40 branched by the optical splitter 30 and transmits an optical signal so as to reach the optical receivers 20A and 20B.

  The optical receiving device 20A is an optical receiving device that collectively receives and identifies optical signals of a plurality of wavelengths regardless of the wavelength, and the optical receiving device 20B receives the optical signals of a plurality of wavelengths for each wavelength and individually identifies them. This is an optical receiver.

  When a signal is transmitted from the optical transmission device 10 to the optical reception device 20A, the wavelength information cannot be identified by the optical reception device 20A within a range where the sum of the received light intensities of the optical signals of the respective wavelengths is the same. Therefore, within the range in which the light reception intensity at the optical receiver 20A is not changed, the encoded information that can be identified only by the optical receiver 20B can be transmitted by controlling and transmitting the transmission signal to the optical receiver 20B. As described above, information can be transmitted simultaneously and independently to the optical receiving apparatuses 20A and 20B of different receiving methods.

<Second embodiment>
In the optical transmission system of the second embodiment, in the optical transmitting apparatus 10 of the first embodiment, ₁ the wavelength of the optical transmitter _{11 1 ~11 n λ, λ 2} , ···, and lambda _n, the m As the number of wavelengths used in the encoding method used in this method, the received light intensity of n + 1 values from the 0 level to the n level that can be taken by the optical receiving apparatus 20A collectively identified is in the range of the received intensity of n + 1-m. The combination of m wavelengths is transmitted as a multi-level code by utilizing the fact that a specific m (m is an integer satisfying 2 ≦ m ≦ n−1) wavelength can be arbitrarily selected.

This is shown in FIG. The combination of ON / OFF state of each optical transmitter ₁₁ 1 to 11 _n, respective wavelengths λ _1, λ _2, ···, the lambda _n, turns ON, the the OFF state (0) (1). In FIG. 2, for example, _n C ₀ is OFF for all of the optical transmitters 11 _{1 to} 11 _n , _n C ₁ is ON for _one of the optical transmitters 11 _{1 to} 11 _n , and the rest is OFF,. , _N C _n indicates that all of the optical transmitters 11 _{1 to} 11 _n are ON.

When transmitting a signal from the optical transmission device 10, there are n + 1 possible intensities that can be obtained by the optical reception device 20A collectively identified. There are _n C _k combinations of transmission wavelengths at that time (k is an integer satisfying 1 ≦ k ≦ m−1). Here, when attention is paid to specific m wavelengths (λ _{n + 1−m} ,..., Λ _n ), _{n + 1−m} from k to k + n−m, in which the reception intensity is not changed by the optical reception device 20A collectively identified. Within the range of received intensity, if there are i (i is an integer satisfying i = k) wave components in the ON state, that is, (1) among the specific m wavelengths, There are _m C _i combinations of possible ON / OFF states. In the receiving device 20B that can be identified for each wavelength, the wavelength of the optical signal can be identified. Therefore, as shown in a portion surrounded by a broken line in FIG. Two codes, ..., _m Ci codes are defined and identified as multi-level codes. As a result, transmission of information to the optical receiver 20B identified for each wavelength becomes possible without affecting the bandwidth of the optical receiver 20A that is collectively identified.

<Third embodiment>
In the optical transmission system of the third embodiment, in the optical transmission system of the first embodiment, a signal is transmitted using the encoding method of the optical transmission system of the second embodiment, and the encoded information is transmitted.

<Fourth embodiment>
FIG. 3 shows an example of the optical transmission system of the fourth embodiment when the number of wavelengths is 3 (n = 3). The optical signal transmitted from the optical transmitter 10 that converts the input from the outside propagates through the optical fiber transmission line 40 and is identified for each wavelength with _three optical receivers 20A _{1 to} 20A 3 that are collectively identified. The signals are received by the _three optical receivers 20B _{1 to} 20B ₃ .

FIG. 4 shows a configuration example of the optical transmission device 10. The multi-level logic converter 15 having the S / P conversion unit of the optical transmitter 10 converts a high-speed binary signal input from the outside into multi-level logic and receives the multi-level code by the batch receiver 20A. A function to convert a binary parallel signal (mark rate of each channel is ½) that can sometimes be received as a multi-level code, and a high-speed binary signal input from the outside to multi-level logic A function for converting the multi-level code into a binary parallel signal (for a conventional multi-level transmission system), a function for converting a high-speed binary electric signal into a plurality of low-speed binary optical signals having different wavelengths (conventional For parallel transmission system). Each of the optical transmitters 11 _{1 to} 11 ₃ modulates an optical signal using each binary signal. The three binary optical signals generated as described above are multiplexed by the wavelength multiplexer 12 and transmitted to the optical fiber transmission line 40.

The optical receiver is as follows. In the optical receivers 20A _{1 to} 20A ₃ that collectively identify, optical signals of all wavelengths are received by the single optical receivers 21 _{1 to} 21 ₃ without using a filter, and are identified as multilevel codes. This is an optical receiver used in a multilevel transmission system. The optical receiving devices 20B _{1 to} 20B ₃ that identify and receive each wavelength include the wavelength demultiplexer 22 and the optical receivers 23 ₁ to 23 _{3 corresponding} to the number of wavelengths that receive the optical signal demultiplexed for each wavelength. . This is an optical receiver used in a parallel transmission system.

Here, in the optical transmitter 10, a signal table as shown in FIG. 5 is prepared. For the combinations of the ON / OFF states of the optical transmitters 11 _{1 to} 11 ₃ , (1) is turned on and (0) is turned off for each of the wavelengths λ ₁ , λ ₂ , and λ ₃ . In the case of the present embodiment, a total of 8 combinations of ON / OFF states can be taken. Among these, in the case of taking a combination of (1, 0, 1), (1, 1, 0), (0, 0, 1), (0, 1, 0), the optical receiver 20A ₁ that identifies all at _once. while transmitting the information to the through 20a _3, an optical receiver _20B 1 _{~20B 3} for receiving identifying for each wavelength (1,0,1) (0,0,1) [1], (1,1 , 0) and (0, 1, 0) are encoded as [0], and information is transmitted to the optical receivers 20B _{1 to} 20B ₃ independently and simultaneously with the signals to the optical receivers 20A ₁ to 20A ₃ .

FIG. 6 shows the combination of the wavelengths of incident light and the received intensity at each receiving apparatus at this time. Optical receiver 20A ₁ when (λ ₁ , λ ₂ , λ ₃ ) is (1, 0, 1), (1, 1, 0), (0, 0, 1), (0, 1, 0) through 20a _{3, 20B} 1 and the input signal at ～20B _3, threshold in the optical receiving apparatus _20A 1 through 20a ₃ (multi-value), lambda ₂ in the optical receiver _20B 1 ~20B _3, λ optical receiver for ₃ The identification codes (binary) of 23 ₂ and 23 ₃ are shown. The outputs of the optical receivers 20A _{1 to} 20A ₃ are proportional to the number of wavelengths of the incident optical signal, and the multilevel level is 1 or 2. At this time, the combination of the optical signals of λ ₂ and λ _{3 in} the optical receivers 20B _{1 to} 20B ₃ is (0, 1) or (1, 0), but (0, 1) is changed to [1], (1,0) to that identifying the [0], without affecting the strength of the multilevel signal received by the optical receiving apparatus _20A 1 through 20a _3, the information to the optical receiving apparatus _20B 1 _{~20B 3} Can communicate.

<Fifth embodiment>
In the optical transmission system of the fifth embodiment, in the optical transmission system of the first embodiment (FIG. 1), the optical transmission device is composed of the optical reception device 20B identified for each wavelength and the optical reception device 20A collectively identified. The signal transmission time from 10 is divided. Within each of the divided signal transmission times, signals are transmitted so that information is transmitted from the optical transmission device 10 to the optical reception device 20A group during the signal transmission time allocated to the optical reception device 20A group. A signal is transmitted so that information is transmitted from the optical transmission device 10 to the optical reception device 10B group by performing S / P conversion on the binary code input to the optical transmission device 10 during the signal transmission time allocated to the device 20B group. Send.

Also, within the signal transmission time of the optical receiver 20A group and within the signal transmission time of the optical receiver 20B group, a signal is transmitted to a user having the same type of optical receiver using the time division multiplexing method. In addition to the above, during the signal transmission time to the group of optical receivers 20A that are collectively identified, the signals to the group of optical receivers 20B are transmitted while being controlled within a range in which the received light intensity in the group of optical receivers 20A is not changed. Thus, encoded information that can be identified only in the optical receiver 20B group can be transmitted. Thus, information can be broadcast to the optical receiver 20B group during the signal transmission time to the optical receiver 20A group, and the band from the optical transmitter 10 to the optical receiver 20B group is increased. In the system described above, when a group of receiving devices different from the identifiable wavelengths is mixed in the receiving device 20B group identified for each wavelength, the transmission time of the encoded information to the receiving devices having different receivable wavelengths is divided. . For _{example, λ 1, λ 2, ···} , and receives a receiving apparatus group to _{λ n, λ 1, λ 2} , ···, λ m (m <n) receives a receiving apparatus group to coexist In this case, different signal transmission times are assigned to the transmission time of encoded information addressed to a group of receiving devices capable of receiving n wavelengths and the transmission time of encoded information addressed to a group of reception devices capable of receiving m wavelengths.

<Sixth embodiment>
In the optical transmission system of the sixth embodiment, in the optical transmission system of the fifth embodiment, a signal is transmitted using the encoding method of the optical transmission system of the second embodiment, and the coded information is transmitted. .

<Seventh embodiment>
The optical transmission system of the seventh embodiment is shown in FIG. Signal transmission times to the optical receivers 20A ₁ to 20A ₃ to be collectively identified communicate using the multi-value transmission method, and are parallel to the signal transmission times to the optical receivers 20B ₁ to 20B ₃ to be identified for each wavelength. Use the transmission method. In signal Okuden time to the optical receiving apparatus _20A 1 through 20a _3, the encoding information for all of the optical receiver _20B 1 _{~20B 3} using the coding method in the second embodiment (FIG. 2) To communicate. When this method is applied, FIG. 7 schematically shows time slots in which the receiving devices 20A _{1 to} 20A ₃ and 20B _{1 to} 20B ₃ receive signals addressed to the own device. a ₁ ~a ₃ the time slot for the optical receiver _{20A 1 ~20A 3, b 1 ~b} 3 the time slot for the optical receiver _20A 1 _{~20A 3,} a is for an optical receiving apparatus _20A 1 through 20a ₃ a time slot for the optical receiving apparatus _20A 1 through 20a ₃ utilizing time slots.

When signals encoded by the optical transmission system according to the second embodiment (FIG. 2) are transmitted to the optical receivers 20B _{1 to} 20B ₃ , the reception strength that the optical receivers 20A _{1 to} 20A ₃ can take is 0 level. Assuming that all of the three levels occur with the same probability, when the reception intensity is 1 level or 2 levels, that is, at the signal transmission time half of the signal transmission time for the optical receivers 20B _{1 to} 20B ₃ , Signal transmission is possible. Since the encoded information is also received by the optical receivers 20B _{1 to} 20B ₃ in the time slot of the multilevel transmission scheme, the bandwidth from the optical transmitter 10 to the optical receivers 20B ₁ to 20B ₃ is the parallel transmission scheme. In addition to this, the encoding information increases.

<Eighth embodiment>
In the optical transmission system of the eighth embodiment, in the optical transmission system shown in the fifth embodiment (system that divides the signal transmission time in FIG. 1), when there are a plurality of optical receivers 20B, the optical transmitter 10 Destination information is added to the encoded information generated from the optical receiver 20B, received on the optical receiver 20B group side, and the received signal is discarded except in the case of the encoded information addressed to the own apparatus. Encoding information is transmitted only to a part of the information.

  The destination information is determined by using an upper layer, and for example, as in the header method, an identifier corresponding to each optical receiver in the optical receiver 20B group is set on the optical transmitter 10 side in the fifth embodiment. The identifier is added to the encoded information in and transmitted. On the optical receiver 20B group side, within the signal transmission time assigned to the optical receiver 20B group, it can be received and decoded only by the optical receiver 20B corresponding to the identifier, and does not correspond to the identifier. In 20B, the received signal is discarded. Thereby, the encoded information is transmitted only to an arbitrary optical receiving device in the optical receiving device 20B.

<Ninth embodiment>
In the optical transmission system of the ninth embodiment, in the optical transmission system of the seventh embodiment, a signal is transmitted using the encoding method of the optical transmission system of the second embodiment, and the encoded information is transmitted.

<Tenth embodiment>
In the optical transmission system of the tenth embodiment, in the optical transmission system of the seventh embodiment, the destination information is added to the encoded information that can be identified only by the optical receivers 20B _{1 to} 20B ₃ transmitted from the optical transmitter 10. In addition, each of the optical receivers 20B _{1 to} 20B ₃ determines the destination information, and discards the received signal having the destination information other than the own apparatus, so that a part of the optical receiver 20B group is discarded. Only carry the encoded information.

The signal reception time in each optical receiver when the optical transmission system of this embodiment is used is as shown in FIG. In the time slot of the multi-level transmission system for transmitting information to the optical receiving apparatus _20A 1 through 20a ₃ A for any of the optical receiver f multicast specified by the destination information of the light receiving device _20B 1 _{~20B 3} or uni, Encoded information can be transmitted in a cast format. In the optical transmission system of the seventh embodiment (FIG. 7), since the destination information is not added, the time slot a is commonly assigned to the optical receivers 20B _{1 to} 20B ₃ , but the optical transmission system of the present embodiment Then, the time slot a is assigned to the one specified by the destination information in the optical receivers 20B _{1 to} 20B ₃ .

It is a block diagram of the optical transmission system of the 1st Example of this invention. It is explanatory drawing of the encoding of the optical transmission system of the 2nd Example of this invention. It is a block diagram of the optical transmission system of 4th Example of this invention. It is a block diagram of the optical transmitter of the optical transmission system of the 4th Example of this invention. It is explanatory drawing of the output pattern of the optical transmitter of the optical transmission system of 4th Example of this invention. It is explanatory drawing of the input pattern of the optical receiver of the optical transmission system of 4th Example of this invention. It is operation | movement explanatory drawing of the optical transmission system of the 7th Example of this invention. It is operation | movement explanatory drawing of the optical transmission system of 9th Example of this invention. It is a block diagram of the conventional optical transmission system of a parallel transmission system. It is a block diagram of the optical transmission system of the conventional multi-value transmission system.

Explanation of symbols

10: optical transmission apparatus 11, 11 ₁ to 11 _n: an optical transmitter 12: a wavelength multiplexer 13: multivalued logic conversion unit 14: S / P conversion unit 15: multivalued logic converter with the S / P converter 20A, 20A _{1 to} 20A _n : Optical receiver (second optical receiver)
20B, 20B _{1 to} 20B _n : Optical receiver (first optical receiver)
21, 21 _{1 to} 21 ₃ : optical receiver 22: wavelength demultiplexer 23, 23 ₁ to 23 ₃ : optical receiver 24: P / S conversion unit 25: threshold value determination unit 26: multilevel binary conversion unit 30: Optical power splitter 40: optical fiber transmission line

Claims (10)

An optical transmission method for multiplexing and transmitting a plurality of optical signals having different wavelengths, which are intensity-modulated and synchronized, and branching the multiplexed optical signal and receiving it by a plurality of optical receivers,
As the plurality of optical receivers, a first optical receiver capable of identifying the intensity of a plurality of optical signals having different wavelengths for each wavelength or all wavelengths of the optical signal transmitted from the optical transmitter; Mix one or more second optical receivers that identify multiple wavelengths at once,
Transmitting from the optical transmission device encoded information that is identified as having the same total received light intensity in the second optical reception device and in which a difference in wavelength combination is identified in the first optical reception device; An optical transmission method characterized by the above. An encoding method used in the optical transmission method according to claim 1,
When transmitting optical signals of n waves of different wavelengths (n is an integer satisfying n ≧ 3) from the optical transmission device,
For specific m-wave optical signals (m is an integer satisfying 2 ≦ m ≦ n−1) among the n-wave optical signals having different wavelengths, 0 to n that can be taken by the second optical receiver. Among the n + 1 received light intensities, the second second light intensity is within a range identified as n + 1−m received light intensities from adjacent k (k is an integer satisfying 1 ≦ k ≦ m−1) to k + nm. Independently of the n + 1−m received light intensity that can be obtained by the optical receiver, any i (i is an integer satisfying i = k) wave of the m-wave optical signals is turned on, and the remaining mi waves are turned on. Control the combination of the ON / OFF state of the n-wave optical signal so that it can be set to OFF,
The second optical receiving apparatus cannot identify, and the first optical receiving apparatus identifies _m C _i combinations of ON / OFF states that can be taken by the specific m wave as a multi-level code of _m C _i values. An encoding method characterized by being transmitted as encoded information. The optical transmission method according to claim 1,
Dividing the optical signal transmission time to the first optical receiver and the optical signal transmission time to the second optical receiver;
In the allocation time to the first optical receiver, a signal is transmitted so as to convey information to the first optical receiver,
In the time allotted to the second optical receiving device, it is received as a multilevel code by the second optical receiving device and received as the encoded information by the first optical receiving device. An optical transmission method comprising transmitting a signal. The optical transmission method according to claim 3.
When a plurality of the first optical receivers are connected, encoded information that can be identified by the first optical receiver is transmitted only to a part of the first optical receiver. An optical transmission method characterized by the above. The optical transmission method according to claim 3.
The optical transmission method according to claim 2, wherein the encoding information is encoding information using the encoding method according to claim 2.   A function of converting a high-speed binary electrical signal into a plurality of low-speed binary optical signals having different wavelengths, combining the plurality of binary optical signals with one optical transmission medium, and receiving by the optical receiver And a function of transmitting encoded information in which the combination of wavelengths is controlled within a range in which the sum of received light intensities is identified as the same. The optical transmission device according to claim 6.
The optical transmission apparatus according to claim 2, wherein the encoded information is information created by the encoding method according to claim 2. One or more first optical receivers that demultiplex a received signal and identify each wavelength using an optical receiver;
One or more second optical receivers that collectively receive signals for a plurality of wavelengths using a single optical receiver and identify them as multi-level codes;
A function of converting a high-speed binary electric signal into a plurality of low-speed binary optical signals having different wavelengths, and combining and transmitting the plurality of low-speed binary optical signals to one optical transmission medium; 1 having a function of controlling the combination of wavelengths within a range in which the total received light intensity is identified to be the same in the optical receiver, and transmitting encoded information that can be identified only to the first optical receiver. An optical transmitter;
An optical transmission system comprising: An optical transmission system using the optical transmission method according to claim 3,
A first optical receiver according to claim 8, a second optical receiver according to claim 8, and an optical transmitter according to claim 8,
The second optical transmission apparatus discards the received signal at a time other than the allocated time,
The first optical receiver has a function of identifying the encoded information within a time allotted to the second optical receiver;
When the optical transmission device converts the high-speed binary electrical signal into a plurality of low-speed binary optical signals having different wavelengths, the optical signal transmission time to the first optical reception device is different for each wavelength. Is converted to a low-speed binary optical signal that can be discriminated into two, and the signal transmission time to the second optical receiver is such that the signal can be identified as a multi-level code when collectively identified. An optical transmission system having a function of converting into a plurality of different low-speed binary optical signals. An optical transmission system using the optical transmission method according to claim 4,
A first optical receiver according to claim 9, a second optical receiver according to claim 9, and an optical transmitter according to claim 9,
The first optical receiving device has a function of identifying and receiving only the information addressed to the own device by identifying the destination of the encoded information,
The optical transmission system has a function of adding destination information to encoded information that can be identified by the first optical receiver and transmitting the encoded information.

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