JP2697208B2 - Two-way transmission between multiple points - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] In the present invention, when bidirectional transmission is performed between a plurality of points, it is possible to collectively amplify optical signals transmitted from each point by one amplifier. It relates to a possible bidirectional transmission method.

[Prior Art] The emergence of an optical communication system for performing bidirectional transmission between a plurality of points has been strongly desired. In order to realize this optical communication system, it is necessary to distribute the optical signal to each point. At that time, the number of distributions is limited or the propagation The distance becomes shorter. To improve this, the optical signal is directly amplified as it is. "Optical amplifiers" must be introduced.

FIG. 4 shows a conventional example of an optical communication system between three points (A, B, and C) using the optical amplifier. In this method, a transmission optical frequency (or transmission wavelength) is individually assigned to each point, and the configuration is such that deterioration of crosstalk due to an optical signal transmitted from each point is suppressed.

[Problems to be Solved by the Invention] According to the conventional point-to-point optical communication system, bidirectional transmission can be performed between point A and point C, and between point B and point C. Reach the point. However, this method has a problem that two-way communication cannot be performed between the point A and the point B. Therefore, the transmission distance between each point cannot be made long. In addition, since the distance between the points varies, there is a problem that the optical reception level of the optical receiver becomes unstable.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a transmission system capable of bidirectional transmission between a plurality of points via one optical amplifier.

[Means for Solving the Problems] The gist of the present invention is to provide a method for bidirectional transmission between stations having at least three stations N via one optical amplifier. One station has one optical transmitting unit and one optical receiving unit, and the optical transmitting unit and the optical receiving unit are connected to one transmission line by a Y-branch unit.
Stations are oppositely connected to the optical amplifier and the remaining (N-
The station 2) has two optical transmitting units and one optical receiving unit, and one of the two optical transmitting units and the optical receiving unit is connected to the optical amplifier of the optical amplifier through a Y branch and one transmission line. In addition to being connected to one side, another optical transmitter and the optical receiver are connected to the other side of the optical amplifier via a Y-branch and one transmission line, and the optical transmitters of the respective stations are different. The optical receiver of each station transmits the optical signal of the adjusted optical frequency, and selectively tunes and receives the optical frequency.

Also, a part of the optical transmission line from each station, an optical amplifier, and a part of the optical transmission path from the optical amplifier to each station are connected to an n-port to m-port type optical star coupler (n-port doped with rare earth element ions). , m: ≧ 3) and a configuration in which an excitation light source is provided at at least one of the ends of the port. In this case, Er ions were used as the rare earth element ions, and the wavelength of the optical signal of each optical transmitter was 1.5 μm.
A band can be used.

Next, when configured as an apparatus, N units (N is an integer of 3 or more) including at least one set of an optical transmission unit and an optical reception unit
Station, at least four optical transmission lines from these stations, and one optical amplifier, and the optical transmission lines from all the other stations except any one station are connected to one terminal side of the optical amplifier. The optical transmission line from one of the removed stations and the optical transmission line from N-1 stations except any one of the other stations are connected to the other terminal side of the optical amplifier. Can be configured by being connected to and connected to.

[Operation] As described above, according to the present invention, one terminal side of an optical amplifier is coupled to and connected to an optical transmission line such as a station A side, a station C side, a station D side, and the other terminal side of the optical amplifier. And transmission lines such as the station B side, the station C side, and the station D side. An optical transmitter and an optical receiver are connected to the end of each optical transmission line, each optical transmitter transmits an optical signal having a different optical frequency, and each optical receiver selectively selects each optical frequency. It has the function of tuning and receiving. With such a configuration, two-way communication can be realized between at least three points.

For example, in the case of three stations A, B, and C, an optical signal (optical frequency f1) from the optical transmitter of the station A is transmitted from the station A to the station B through the optical amplifier to the optical receiver of the station B. On the contrary, the transmission of the optical signal (optical frequency f2) from the station B to the station A is also possible by following the route in the reverse direction.

Next, it is possible from the station A to the station C by transmitting an optical signal (optical frequency f1) from the optical transmission unit of the station A to the optical reception unit of the station C through an optical amplifier. The reverse transmission from the station C to the station A is possible by transmitting the optical signal (optical frequency f3) from the optical transmission unit of the station C to the optical reception unit of the station A through the reverse path. is there.

Similarly, bidirectional transmission between stations B and C is possible by using a path through an optical amplifier.

Since the bidirectional transmission between any of the above stations is performed only through one common optical amplifier, the receiving sensitivity becomes uniform.

Embodiment FIG. 1 shows an embodiment of a method and apparatus for bidirectional transmission between plural points according to the present invention. This embodiment has a configuration in which bidirectional transmission can be performed between three stations A, B, and C, and each station has at least one optical transmitting unit and optical receiving unit.

That is, the optical transmitting unit 11 and the optical receiving unit 21 of the station A are Y branching devices.
Optical transmission line 41 (optical fiber) that is coupled by 51 optical coupling circuits
And input to one terminal side of the optical amplifier 3. The optical transmitting unit 12 and the optical receiving unit 22 of the station B are also coupled by the optical coupling circuit of the Y-branch unit 54, connected to the optical transmission line 42 (optical fiber), and input to the opposite terminal side of the optical amplifier 3. . Station C
The optical transmission lines 44 and 43 are connected to one terminal side and the other terminal side of the optical amplifier 3. That is, the optical transmitting unit 13 and the optical receiving unit 23 are coupled by the Y-branches 55 and 57 and connected to the optical transmission line 43, and the optical transmitting unit 14 and the optical receiving unit 23 are coupled to the Y-branching units 56 and 5,
It is configured to be coupled at 7 and connected to the optical transmission line 44. Each of the optical transmitters 11, 12, 13, and 14 transmits an optical signal having a different optical frequency, and each of the optical receivers 21, 22, and 23 has a function of selectively tuning and receiving each optical frequency. doing.

In the above configuration, bidirectional transmission is performed as follows.

First, from the station A to the station B, the optical signal (optical frequency f1) from the optical transmission unit 11 is transmitted to the Y branch 51, the optical transmission line 41, the Y branch 52, the optical amplifier 3, the Y branch 53, and the optical transmission line. This is performed by being sent to the optical receiver 22 through 42 and the Y branch 54. Conversely, from station B to station A, the optical signal (optical frequency f2)
Branch unit 54, optical transmission line 42, Y branch unit 53, optical amplifier 3, Y branch unit 52,
This is performed by being transmitted to the optical receiving unit 21 through the optical transmission line 41 and the Y branch 51.

Next, from the station A to the station C, the optical signal (optical frequency f1) from the optical transmitter 11 is transmitted to the Y branch 51, the optical transmission line 41, the Y branch 52, the optical amplifier 3, the Y branch 53, and the optical transmission line. This is performed by sending the light to the optical receiver 23 through the path 43 and the Y-branches 55 and 57. In the case of the reverse transmission from the station C to the station A, the transmission is performed by transmitting the optical signal (optical frequency f3) from the optical transmission unit 13 to the optical reception unit 21 through the reverse path.

Similarly, the bidirectional transmission between stations B and C is based on the Y branch 54,
Optical transmission line 42, Y-branch unit 53, optical amplifier 3, Y-branch unit 52, optical transmission line 4
4. This is performed by using the path of the Y branch 56. That is, bidirectional transmission between any stations is performed via one common optical amplifier 3.

FIG. 2 shows an embodiment of a method and apparatus configuration for bidirectional transmission between four stations A, B, C and D. The difference from FIG. 1 is that instead of the Y-branches 52 and 53 of FIG.
61 and 62 are provided, and the station d is additionally connected by the transmission lines 46 and 45. The station D, like the station C, couples the optical transmitting unit 15 and the optical receiving unit 24 with Y branching devices 58 and 60 to connect to the optical transmission line 45, and connects the optical transmitting unit 16 and the optical receiving unit 24 to the Y line. Turnout 5
The configuration is such that the optical transmission line 46 is connected by coupling at 9,60. Thus, stations A and D, stations B and D, stations C and D, and station A
And station B, station A and station C, and station B and station C.

Two-way transmission between five or more stations can be realized by increasing the number of branches of the three-branch units 61 and 62 shown in FIG. Become.

In the above embodiment, an optical isolator for suppressing reflected return light may be built in the optical transmission unit. The configuration of the optical receiving unit may be a configuration including a variable optical frequency filter, an optical amplifier, or the like, or a configuration using an optical heterodyne or optical homodyne detection method. As the optical amplifier, a semiconductor laser amplifier (resonant type, traveling waveform, etc.) or an optical fiber amplifier can be used.

FIG. 3 shows another embodiment of the method and apparatus for bidirectional transmission between plural points according to the present invention. This shows the bidirectional transmission direction and device configuration between the three points A, B and C. Er ions were added instead of the Y-branches 52 and 53 and the optical amplifier 3 in FIG. n port vs. m port (n, m: ≧
3) type optical star coupler 7, excitation light sources 81 and 82, optical transmission line 47
And 48. Although two excitation light sources are used, one excitation light source may be used.

In this configuration, the wavelength band of the optical transmitter is 1.53 to 1.56 μm
A belt is used. The wavelength of the excitation light source is 0.98 μm, 1.
46 to 1.48 μm, or 0.83 μm, 0.51 μm, 0.65 μm, or the like is used.

The optical star coupler 7 doped with Er ions may be of an optical fiber type or a waveguide type. Further, an ion co-added with ions such as Yb and Nd other than Er ion may be used. The rare earth element ions to be added into the optical star coupler 7 vary depending on the transmission wavelength of the optical transmission unit, and may be those containing at least one kind of ions such as Er, Nd, Sm, Ho, Tm, and Tb. Further, the number of input / output ports of the optical star coupler 7 may be increased, the number of pump light sources may be further increased, and the gain of the optical amplifier may be increased.

[Effects of the Invention] As described above, according to the present invention, since bidirectional transmission can be performed between at least three points via one optical amplifier, the reception sensitivity of the optical receiver is long and uniform. Can be kept.

[Brief description of the drawings]

1 to 3 show an embodiment of a method and apparatus for transmitting data between plural points according to the present invention, respectively, and FIG. 4 shows the structure of a conventional bidirectional transmission system between plural points. In the figure, 3 is an optical amplifier, 11 to 16 are optical transmitters, 21 to 24 are optical receivers, 41 to 46 are transmission lines, 51 to 60 are Y-branches, 61 and 62 are three-branches, and 7 is Optical star coupler doped with Er ions, 8
1,82 indicates an excitation light source.

Claims (1)

(57) [Claims] 1. A method for bi-directionally transmitting between stations each having at least three stations N through one optical amplifier, the two stations comprising one optical transmitting unit and one optical transmitting unit. The optical transmitter and the optical receiver are connected to one transmission line by a Y-branch device, the two stations are connected to the optical amplifier in opposition, and the remaining (N-2) Stations each have two optical transmitters and one optical receiver,
One of the optical transmitters and the optical receiver is connected to one side of the optical amplifier via a Y-branch and one transmission line, and the other optical transmitter and the optical receiver are Y-branch. Bowl and 1
Connected to the opposite side of the optical amplifier via two transmission lines, the optical transmitter of each station transmits an optical signal of a different optical frequency, and the optical receiver of each station selectively tunes the optical frequency. A two-way transmission method between a plurality of points.