JPH09270745A - Optical signal transmitter and optical communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To relax the limit of the frequency band of the communication optical signal of a subscriber by generating continuously the light of a pseudo light source with a prescribed luminous intensity or over and applying modulation to the light so as to obtain a transmission optical signal. SOLUTION: An optical signal transmitter 42 receives an optical signal 10 of '101010101100110001100010' as a reception signal. The received optical signal 10 is distributed into 8 in total as distributed signals 12 and they are shifted one by one bit sequentially and then summed to obtain a pseudo light source light 18, which is outputted from an optical signal confluent device 20. A modulator 2 modulates the light source light 18 and the result is outputted as a transmission optical signal 28. Since a prescribed luminous intensity or over is continuous in the light source light 18, the frequency band of the signal 28 is not restricted by the frequency band of the received light 10. When the mark rate of the received light is closer to 1/2, the transmission amount is more and the fluctuation in the luminous intensity of the pseudo light source section 24 is in general less. Moreover, the less number of consecutive 0 bits of the reception optical signal 10 is, the less the luminous intensity of the pseudo light source section 24 is fluctuated.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to optical communication.

[0002]

2. Description of the Related Art Conventionally, in a digital optical communication network connecting a station and a subscriber, there is known an optical communication system in which a light source is not provided in an optical communication device on the subscriber side. No light source is provided because the light source is generally expensive and fragile. In this optical communication system, the optical signal received by the subscriber side (hereinafter, received optical signal) is reused as a light source of the optical signal transmitted from the subscriber side (hereinafter, transmitted optical signal).

In the reuse of the received optical signal, a plurality of bits of the received optical signal consisting of a binary signal of "1 level" or "0 level" are set as one time slot in the transmitter on the subscriber side, and this time slot is used. It is modulated for each to make a transmission optical signal. Specifically, when transmitting a "0 level" time slot, all bits in the time slot are modulated to "0 level" and output. Then, in the receiving device on the station side that receives this transmitted optical signal,
If all the bits in one time slot are "0 level", the level of the time slot is judged to be "0 level". On the other hand, even if 1 bit has "1 level" bit in one time slot, The level of the time slot is determined to be "1 level". As a result, the transmitted optical signal is
"1 level" or "0 level" for each time slot
Can be treated as a binary signal having a value of.

[0004]

However, when all the bits in one time slot are "0 level" from the beginning, that time slot cannot be set to "1 level" even if modulation is applied. Therefore, in the above-described conventional optical communication system, bi in one time slot is
The number of t is the maximum continuous bit of 0 level in the received optical signal.
It needs to be greater than the number. As a result, when the maximum number of consecutive bits at the 0 level is r, the upper limit of the band of the transmission optical signal is limited to 1 / r of the band of the reception optical signal. For example, in the case of r = 100 or r = 1000, the upper limit of the band of the transmitted optical signal, especially the frequency, is lowered by two or three digits compared with the band of the received optical signal.

Therefore, a light source is not provided in the communication device on the subscriber side, and the optical signal transmission device and the optical communication system using the same, in which the restriction on the band of the transmission optical signal of the communication device on the subscriber side is relaxed. Has been desired.

[0006]

[Means for Solving the Problems]

(First Invention) According to the optical signal transmitter of the first invention of this application, a received optical signal consisting of a binary optical signal of "0 level" or "1 level" is converted into 0 of this received optical signal. The distribution means for dividing the distribution signal into a larger number of distribution signals than the maximum number of consecutive bits, the delay means for delaying the distribution signal by different times, and the distribution signals delayed respectively are combined to obtain a light intensity of a certain level or more. It is characterized in that it comprises a confluence means for continuously outputting the pseudo light source light and a modulation means for modulating the pseudo light source light.

According to the optical transmitter of the first aspect of the present invention, the pseudo light source light having a light intensity equal to or higher than a certain level is continuously generated, and this light is modulated to be a transmission optical signal. Therefore, the length of one time slot can be set to be equal to or less than the length of one bit of the received optical signal regardless of the maximum number of 0-level continuous bits of the received optical signal. As a result, the band limitation of the transmission optical signal on the subscriber side can be relaxed.

In the optical signal transmitter of the first invention, preferably, the distributing means is a 1 × m optical coupler (m is a natural number) and a plurality of optical couplers connected in series to the 1 × m optical coupler. The merging means is composed of an n × 1 optical coupler (n is a natural number).
m delay means is provided between the optical coupler and the optical coupler, delay means is respectively provided between the optical couplers connected in series, and delay means is provided between the optical coupler and the n × 1 optical coupler. It is desirable to have it.

If an optical coupler is used, it is possible to use a combination of delay means provided in series via the optical coupler. As a result, the delay means can be reduced. For example, when a delay loop is used, the layer extension of the delay loop can be shortened.

(Second Invention) According to the optical communication system of the second invention related to this application, the optical communication system comprises a station side communication device and a subscriber side communication device, and the station side communication device is a station side receiving device. And a station-side transmitter equipped with a light source for transmitting an optical signal, and the subscriber-side communication device is a distributor to which a received optical signal from the station-side transmitter is input, and a distributor by the distributor. In an optical communication system comprising a subscriber-side receiving device that receives one of the received optical signals, and a subscriber-side transmitting device that receives the other received optical signal distributed by this demultiplexing region, The subscriber-side transmitting device is configured by the optical signal transmitting device of the first invention.

As a result, the restriction on the band of the transmission optical signal of the communication device on the subscriber side can be relaxed.

By the way, as described above, in the conventional optical communication system, the subscriber side is not provided with the light source, and the station side receiving device is required to have a special function. This special function is, for example, 1 bi in 1 time slot.
If there is a bit of "1 level" even at t, it means a function of judging the level of the time slot as "1 level". In this respect, in the optical communication system of the second invention,
Such a special function is not required for the station receiver of the station communication device.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an optical signal transmitting apparatus of a first invention according to this application and an optical communication system of a second invention using the same will be described below with reference to the drawings. . It should be noted that the drawings to be referred to are merely schematic representations to the extent that the invention can be understood, and are merely schematic representations of the sizes, shapes, and positional relationships of constituent components of the invention. Therefore, these inventions are not limited to the illustrated examples.

(First Embodiment) In the first embodiment, an example of the optical signal transmitting apparatus of the first invention and the optical communication system of the second invention using the same will be described together.

First, FIG. 1 shows a schematic diagram of an optical signal transmitter according to a first embodiment. According to this optical signal transmitter, the received optical signal 10 composed of the binary optical signal of "0 level" or "1 level" is distributed more than the maximum continuous bit number of 0 level of the received optical signal 10. The optical signal distributor 14 is divided into 12 and the optical signal distributor 14 is provided. The delay signal 16 is provided as delay means 16 for delaying the distributed signal 12 by different times, and the delayed distributed signals 12 are merged. The optical signal combiner 20 is provided as the joining means 20 for continuously outputting the pseudo light source light 18 having a light intensity equal to or higher than a certain level, and the modulator 22 is provided as the modulating means for modulating the pseudo light source light 18. There is.

For example, when the maximum number of 0-level continuous bits of the received optical signal 10 is 4, the signals are distributed to eight distribution signals 12 that are more than four here. Each distributed signal 12 is delayed by a delay loop 16 for different times. The first-stage distributed signal 12a has a delay time of 0, the second-stage distributed signal 12b has a delay time of 1 bit, the n-th distributed signal has a delay time of nbit, and the eighth-stage distributed signal 12h has a delay time of nbit. 8 bits and 1 bit are sequentially delayed. Further, in FIG. 1, the delay loop 16 for one round per 1-bit delay is shown. In FIG. 1, the optical signal distributor 14, the delay loop 16, and the optical signal combiner 20 are shown together as a pseudo light source unit 24.

Further, since the pseudo light source light 18 is obtained by merging the distributed signals 12 having a delay stage number larger than the maximum continuous bit number of the 0 level of the received light signal 10, the start portion s described later is used. Except for this, at least one of the demultiplexed signals 12 is always at one level. The one-level light intensity P ₁ of one distributed signal is approximately equal to the one-level light intensity P ₀ of the received optical signal divided by the number of distributions. Therefore, in the pseudo light source light 18, the light intensity of P ₁ or more is continuously output.

Further, when using the pseudo light source light 12, it is desirable to use it except the start section indicated by s in FIG. This is because in the start section s, only a part of the distributed signals 12 having a short delay time is output from the distributed signals 12 of a total of eight stages, so that the light intensity is weak and sometimes the light intensity is 0 level. Because. Therefore, it is preferable that the pseudo light source light 18 generate the transmission light signal 28 by modulating the portion after the distribution signals 12 of all stages are aligned and the light intensity becomes more stable.

In this embodiment, an optical signal "101010101100110001100010" is received as the received optical signal 10. The distributed signal 12 obtained by branching the received optical signal 10 is sequentially shifted by 1 bit to make a total of 8 stages, and the sum is added and output as the pseudo light source light 18 from the optical signal combiner 20. The height of the pseudo light source light 18 schematically shown in FIG. 1 indicates the light intensity (relative value). Then, the pseudo light source light 18 is modulated by the modulator 22 and output as a transmission light signal 28. Here, an optical signal “1011010100110111001” is transmitted as the transmission optical signal 28. Since the pseudo light source light 18 has a continuous light intensity of a certain level or more, the band of the transmission light signal 28 is not restricted by the band of the reception light signal 10.
Therefore, for example, the band of the transmission optical signal 28 is set to the reception optical signal 2
It can also be higher than the zero band.

In addition, the larger the number of stages for distributing and delaying the received optical signal, the smaller the fluctuation of the light intensity of the pseudo light source light in general. Further, the mark ratio of the received optical signal is preferably close to 1/2 because the amount of transmitted signal is large and the fluctuation of the light intensity of the pseudo light source light is generally small. In addition, the smaller the number of 0-level continuous bits of the received optical signal, the smaller the fluctuation of the light intensity of the pseudo light source light in general.

Next, FIG. 2 shows a block diagram of an optical communication system using the optical signal transmitter of the first embodiment. According to this optical communication system, the station side communication device 30 and the subscriber side communication device 3 connected to each other via the optical fiber 26.
2 and. And this station side communication device 30
Station receiver 34 and light source 35 for transmitting optical signals
And a station-side transmitter 36. The subscriber-side communication device 32 includes a distributor 38 to which the received optical signal 10 from the station-side transmitter 36 is input, and the distributor 38.
The subscriber side receiving device 40 receives one of the received optical signals 10 distributed by, and the subscriber side transmitting device 42 to which the other received optical signal 10 distributed by the distributor 38 is input. There is.

Further, in this optical communication system, the subscriber side transmission device 42 is constituted by the optical signal transmission device 44 described in the above-mentioned first embodiment. Therefore, the transmission optical signal 2 output from the subscriber communication device 32
The band constraint of 8 is relaxed. In FIG. 2, the pseudo light source unit 24 is displayed as a light source unit.

(Second Embodiment) In the second embodiment, an example in which an optical coupler is used in the optical signal transmitter of the first invention will be described.

FIG. 3 shows a schematic diagram of an optical signal transmitter according to the second embodiment. According to this optical signal transmitter 50,
The distributing means is a 1 × 2 optical coupler 52 and a three-stage 2 × 2 optical coupler 5 connected in series to the 1 × 2 optical coupler 52.
4, 56 and 58. Further, the merging means is constituted by a 2 × 1 optical coupler 60. A delay means 62 is provided between the 1 × 2 optical coupler 52 and the first stage 2 × 2 optical coupler 54, and the delay unit 62 is provided between the 2 × 2 optical couplers connected in series (the first stage (Between the second stage and between the second stage and the third stage), and delay means 64 and 66, respectively, and the 2 × 2 optical coupler 5 at the third stage
A delay means 68 is provided between the 8 and the 2 × 1 optical coupler 60. In FIG. 1, the 1 × 2 optical coupler 52, the 2 × 2 optical couplers 54, 56 and 58, the 2 × 1 optical coupler 60, the delay units and the paths are shown as a pseudo light source unit 72.

The 1 × 2 optical coupler 52 and the first stage 2
The × 2 optical coupler 54 is connected to the first path 70a having no delay means and the second path 70b having a delay loop 62 for one (= 2 ⁰ ) rounds. When the optical signal makes one round in the delay loop, a 1-bit length delay of the received optical signal occurs as compared with the case where the optical signal does not pass through the delay loop. Therefore, the optical signal passing through the second path 70b is delayed by 1 bit from the optical signal passing through the first path 70a.

Further, the 2 × 2 optical coupler 54 in the first stage and the 2 × 2 optical coupler 56 in the second stage correspond to the third paths 70c and 2 (= 2 ¹ ) loops without the delay means. They are connected by the fourth path 70d provided with the delay loop 64. Therefore, the optical signal passing through the fourth path 70d is delayed by 2 bits from the optical signal passing through the third path 70c.

The second-stage 2 × 2 optical coupler 56 and the third-stage 2 × 2 optical coupler 58 correspond to the fifth paths 70e and 4 (= 2 ² ) rounds which are not provided with delay means. They are connected by a sixth path 70f provided with a delay loop 66. Therefore, the optical signal passing through the sixth path 70f is delayed by 4 bits from the optical signal passing through the fifth path 70e.

Further, the second stage 2 × 2 optical coupler 58 and 2 × 2
The one-optical coupler 60 is connected by a seventh path 70g having no delay means and an eighth path 70h having a delay loop 68 for 8 (= 2 ³ ) rounds. Therefore, the optical signal that has passed through the eighth path 70h is
It is delayed by 8 bits from the optical signal passing through g.

Therefore, this first, third, fifth and seventh
The delay of the optical signal passing through the path is 0 bit. Further, the delay of the optical signal that has passed through the second, third, fifth and seventh paths is 1 bit. In addition, the delay of the optical signal that has passed through the first, fourth, fifth, and seventh paths is 2 bits. In addition, a delay of 20 (= 2 + 4 + 6 + 8) bits at maximum can be generated when passing through the second, fourth, sixth, and eighth routes.

As described above, by using the optical coupler, it is possible to combine the paths of the optical signals to obtain from 0 bit to 20 bit.
Can be delayed by each bit. Then, the 2 × 1 optical coupler adds up the distributed signals of the respective delay times to generate pseudo light source light. This pseudo light source light is modulated by the modulator 22 to be transmitted optical signal 2
It becomes 8. In FIG. 3, the 1 × 2 optical coupler 52, each 2 ×
2 optical couplers 54, 56 and 58, 2 × 1 optical coupler 6
0, each delay means and each path are combined to form the pseudo light source unit 72.
Is shown as.

As described above, if the optical coupler is used, the delay means provided in series via the optical coupler can be used in combination. As a result, the delay means can be reduced. For example, when a delay loop is used as the delay means, the total length of the delay loop can be shortened as compared with the case of the first embodiment.

The optical signal transmitter of the second embodiment is also suitable for use as a transmitter on the subscriber side of an optical communication system, as in the first embodiment.

Although the 1 × 2 optical coupler is used as the optical signal distribution means here, for example, a 1 × 3 optical coupler may be used. A 3 × 4 optical coupler can also be used as the first-stage optical coupler.

(Third Embodiment) In the third embodiment, an example of distributing the received optical signal for each wavelength component in the optical signal transmitting apparatus of the first invention will be described.

FIG. 4A is a schematic diagram for explaining the optical signal transmitting apparatus of the third embodiment. According to this optical signal transmitter 80, the distribution means is configured by the wavelength demultiplexer 82 that outputs the distribution signals of the wavelength components different from each other, while the merging means is the wavelength that combines the distribution signals. It is configured with a multiplexer 84.

Here, FIG. 4B shows the wavelength distribution of the received optical signal and the wavelength component of the distributed signal by the wavelength demultiplexer 80. The horizontal axis of the graph in FIG. 4 represents wavelength (relative value),
The vertical axis represents the light intensity (relative value). The curve I in the graph shows the wavelength distribution of the received optical signal 10. Then, the wavelength demultiplexer 80 divides the received optical signals having wavelengths near the peak of the wavelength distribution I by 8 from a to h in ascending order of wavelength.
It is split into two wavelength components. Then, the distributed signal of the wavelength component a is supplied to the first-stage path 86a not provided with the delay means.
And enters the wavelength multiplexer 84. Further, the distributed signal of the wavelength component b enters the wavelength multiplexer 84 via the second-stage path 86b provided with the delay loop 88 for one round. It should be noted that one round of the delay loop causes a delay of 1 bit length of the received optical signal as compared with the case where the delay loop is not passed. Similarly, the distribution signals of the wavelength components c to h also enter the wavelength multiplexer 84 with the delay sequentially increased by 1 bit. The distribution signal of the wavelength component h is 7b compared to the distribution signal of the wavelength component a.
It causes a delay of it.

Then, the wavelength multiplexer 84 multiplexes the delayed distribution signals of the respective wavelength components and outputs the pseudo light source light. The pseudo light source light is modulated by the modulator 22 and becomes a transmission light signal 28. In FIG. 4, the wavelength demultiplexer 82, the wavelength multiplexer 84, each delay unit, and each path are shown as a pseudo light source unit 90.

Here, the delay time is set longer in the order of the wavelength of the distributed signal of each wavelength component, but the delay time can be set regardless of the order of the length of the wavelength. For example,
It is also possible to lengthen the delay time in ascending order of wavelength.

In each of the above-described embodiments, these inventions have been described only with respect to examples in which a specific material is used and are configured under specific conditions. However, many modifications and variations can be made to these inventions. For example, in the above-described embodiment, an example in which one station-side communication device and one subscriber-side communication device are connected has been described, but these inventions include one or more stations and one or more subscribers. It is suitable for use in an optical communication system for connecting with a person.

Although the delay loop is used as the delay means in each of the above-mentioned embodiments, the delay means is not limited to this, and for example, reflected light is used to increase the optical path length. It can also be used as a delay means by changing it.

[0041]

According to the optical transmitter of the first aspect of the present invention, the pseudo light source light having a light intensity equal to or higher than a certain level is continuously generated and modulated to be a transmission optical signal. Therefore, the length of one time slot can be set to be equal to or less than the length of one bit of the received optical signal regardless of the maximum number of 0-level continuous bits of the received optical signal. As a result, the band limitation of the transmission optical signal on the subscriber side can be relaxed.

If optical couplers are used for the distributing means and the merging means, the delay means provided in series via the optical couplers can be used in combination. As a result, the delay means can be reduced. For example, when a delay loop is used, the layer extension of the delay loop can be shortened.

Further, in the optical communication system of the second invention, the subscriber side transmitter is constituted by the optical signal transmitter of the first invention. As a result, the restriction on the band of the transmission optical signal of the communication device on the subscriber side can be relaxed. Further, the station side receiver is not required to have a special function as in the conventional example described above.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining an optical signal transmitter according to a first embodiment.

FIG. 2 is a block diagram for explaining an optical communication system according to the first embodiment.

FIG. 3 is a schematic diagram for explaining an optical signal transmitter according to a second embodiment.

FIG. 4A is a schematic diagram for explaining an optical signal transmitter according to a third embodiment, and FIG. 4B is for explaining a wavelength distribution of a received optical signal and a wavelength component of a distribution signal. It is a graph.

[Explanation of symbols]

 10: Received optical signal 12: Distribution signal 14: Distribution means (optical signal distributor) 16: Delay means (delay loop) 18: Pseudo light source light 20: Joining means (optical signal combiner) 22: Modulating means (modulator) 24: Pseudo light source part 26: Optical fiber 28: Transmission optical signal 30: Station side communication device 32: Subscriber side communication device 34: Station side receiving device 35: Light source 36: Station side transmitting device 38: Distributor 40: Subscriber Side receiving device 42: Subscriber side transmitting device (optical signal transmitting device) 50: Optical signal transmitting device 52: 1 × 2 optical coupler 54: 1st stage 2 × 2 optical coupler 56: 2nd stage 2 × 2 optical coupler Coupler 58: Second stage 2 × 2 optical coupler 60: 2 × 1 optical coupler 62, 64, 66, 68: Delay means (delay loop) 70a: First path 70b: Second path 70c: Third Route 70d: Fourth route 70e: Fifth route 70 f: Sixth path 70g: Seventh path 70h: Eighth path 72: Pseudo light source unit 80: Optical signal transmitter 82: Wavelength demultiplexer 84: Wavelength multiplexer 86a: First stage path 86b: 2nd stage route 86c: 3rd stage route 86d: 4th stage route 86e: 5th stage route 86f: 6th stage route 86g: 7th stage route 86h: 8th stage route 88: Delay Loop 90: Pseudo light source

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H04B 10/06

Claims (3)

[Claims] 1. Distributing means for splitting a received optical signal consisting of a binary optical signal of "0 level" or "1 level" into a number of distributed signals which is larger than the maximum continuous bit number of 0 level of the received optical signal. Delay means for delaying the distribution signal by different times, merging means for combining the delayed distribution signals, and continuously outputting pseudo light source light having a light intensity higher than a certain level, and the pseudo light source light An optical signal transmitting device, comprising: 2. The optical signal transmitting apparatus according to claim 1, wherein the distributing means comprises a 1 × m optical coupler (m is a natural number) and a plurality of optical couplers connected in series to the 1 × m optical coupler. The merging means is constituted by an n × 1 optical coupler (n is a natural number), and the delay means is provided between the 1 × m optical coupler and the optical coupler. An optical signal transmitting device comprising the delay means between the optical couplers connected in series, and the delay means between the optical coupler and the n × 1 optical coupler. 3. A station-side communication device and a subscriber-side communication device, the station-side communication device comprising a station-side receiver and a station-side transmitter having a light source for transmitting an optical signal, The subscriber-side communication device includes a distributor to which a received optical signal from the station-side transmitter is input, a subscriber-side receiver that receives one of the received optical signals distributed by the distributor, and An optical communication system comprising a subscriber side transmitting device to which another received optical signal distributed by a wave band is input, wherein the subscriber side transmitting device comprises the optical signal transmitting device according to claim 1. An optical communication system characterized by being configured.