JP3040620B2 - Channel selection method in optical frequency division multiplex transmission - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a channel selection method for performing optical frequency division multiplex transmission in a coherent lightwave communication system.

A coherent lightwave communication system has improved reception sensitivity by 10 to 20 dB as compared with conventional intensity modulation / direct detection (IM / DD), and is easy to perform optical frequency division multiplexing. It is expected that the applied practical system will be realized. For example, when an optical fiber transmission line is laid in a subscriber system to provide an information providing service or the like by optical frequency division multiplexing, a simple channel selection method is required to enable reception of a desired channel.

[0003]

2. Description of the Related Art In a network to which optical frequency division multiplexing is applied, an optical signal from a sender is sent out to the network and then subjected to power amplification and passive branching.
Sent to recipient. The receiver selectively reproduces necessary transmission information based on the received optical signal.

Conventionally, as a method for selectively reproducing transmission information, an optical method of selecting a channel at the stage of an optical signal using a wavelength-variable optical filter or the like, a photodiode having a square-law detection characteristic, or the like is conventionally used. A method has been proposed in which channel selection is performed at the stage of an intermediate frequency signal obtained by heterodyne detection.

[0005]

In such a network, if there are a plurality of subscribers on the transmitting side, even if they are assigned different optical frequencies,
There is a problem in that the receiving subscriber cannot determine whether the transmission information is addressed to itself, and it is difficult for the subscriber to select a channel.

Accordingly, an object of the present invention is to provide a simple channel selection method in optical frequency division multiplex transmission.

[0007]

According to the channel selection method of the present invention, a plurality of subscribers having at least one of an optical transmission function and an optical reception function are connected by an optical fiber transmission line, and different transmission subscribers are provided. In an optical frequency division multiplexing transmission system in which optical carriers of a frequency are allocated, a transmitting subscriber performs angle modulation of the above optical carrier with transmission information and intensity modulation with a destination code for designating a destination subscriber. This is a method in which the subscriber on the receiving side determines the subscriber on the transmitting side based on the destination code and reproduces desired transmission information.

Another channel selection method according to the present invention is directed to an optical frequency division multiplexing transmission system in which a plurality of subscribers having at least one of an optical transmission function and an optical reception function are connected by an optical fiber transmission line. An optical frequency is allocated to the pair of subscribers according to the combination of the above, a transmitting side subscriber modulates an optical carrier of the allocated optical frequency by transmission information, and a receiving side subscriber scans a receiving frequency to transmit a signal on the transmitting side. The subscriber is identified and the desired transmission information is reproduced.

[0009]

According to the former method of the present invention, the transmitting side subscriber modulates the angle of the optical carrier by the transmission information and modulates the intensity by the transmission destination code for designating the transmission destination subscriber. Both the transmission information and the destination code can be carried on the same optical carrier, and the subscriber on the receiving side can determine the subscriber on the transmitting side based on the destination code. As a result, simple channel selection becomes possible.

According to the latter method of the present invention, an optical frequency is assigned to a pair of subscribers involved in a combination of transmission and reception, so that the receiving subscriber detects the optical frequency to transmit the signal. Side subscriber can be determined,
Discriminative channel selection becomes possible.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a network to which the present invention can be applied. Some remote terminals RT are provided in the middle of the optical fiber transmission line laid in a ring type,
One or more subscribers are connected to each of these remote terminals RT.

When one subscriber is connected to a remote terminal RT provided in the middle of the ring type optical fiber transmission line, the subscriber is directly connected to the corresponding remote terminal RT by an optical fiber transmission line, When a plurality of subscribers are connected to the remote terminal RT provided in the middle of the ring-type optical fiber transmission line, these subscribers are connected to the remote terminal RT via another remote terminal RT. Connected to the corresponding remote terminal RT.

In this example, the optical signal flows counterclockwise in the ring-shaped optical fiber transmission line, and flows upward and downward between the remote terminal RT and each subscriber in the ring-shaped optical fiber transmission line.

In the following description, four subscribers A, B, C, and D are selected from these subscribers, and different optical frequencies f _A , f _B , f _C , and f _D are assigned to each of them. Shall be

FIG. 2 is a block diagram showing an example of the configuration of the transmitting unit of each subscriber. In this embodiment, the transmission information supplied to the LD drive circuit 2 is subjected to packet processing, and the LD drive circuit 2 supplies the laser diode 4 with a drive current whose current value changes in time series.

The light output from the laser diode 4 which is directly modulated by the drive current is the light which has been angle-modulated (frequency-modulated or phase-modulated). The signal is modulated and transmitted from the transmitting unit.

The operation of the optical modulator 6 is controlled by a modulator driving circuit 8, and intensity modulation in the optical modulator 6 is based on a destination code for designating a destination subscriber.

The modulator driving circuit 8 controls the optical modulator 6 based on the information on the driving state from the LD driving circuit 2 so that the optical modulator 6 performs intensity modulation at a timing corresponding to the header portion of the packet.

FIG. 3 is a diagram showing an example of a packet of transmission information. In this embodiment, each packet is configured by arranging a header section and a data section in this order in time series. The intensity modulation in the optical modulator 6 of FIG. 2 can be performed on the header part of the packet.

When the intensity modulation by the destination code is performed only on the header portion of the packet, the intensity modulation state and the intensity non-modulation state are repeated, and when the AC coupling method is adopted in the receiving section, Since inconvenience occurs, in such a case, the data portion of the packet should be intensity-modulated with a scramble signal. In this case, the modulation degree of the intensity modulation by the scramble signal and the modulation degree of the intensity modulation by the transmission destination code are set to be substantially equal.

Since the intensity modulation and the angle modulation can be superimposed on one optical carrier, the intensity modulation based on the destination code may be performed on the header part and the data part of the packet.

Now, subscribers A, B, C, and D in FIG.
Optical frequency f different from each other_A, F _B, F_C, F_DIs
An example of the operation will be described assuming that it is assigned.
When a signal is sent from subscriber A on the transmitting side to subscribers B, C, and D
In this case, the transmission information is transmitted as described with reference to FIGS.
Packet processing and optical frequency f_ASend by Packet header
The intensity modulated signal of the code assigned to the destination
Superimpose.

Consider a case in which a subscriber B receives a message. Subscriber
B is the optical frequency f_A, F_C, F_DReceive the light. FIG.
It is a figure showing an example of composition of a receiving part of a visitor. Light beam to subscriber B
Wave number f_A, F _C, F_DWhen the optical signal of
Is split by the optical splitting circuit 10 and the monitor system 12
It is supplied to the selective receiving system 14 respectively. Selective reception system 1
4 has a plurality of selective light receivers 16A, 16B,.
You.

In the monitor system 12, the optical frequency is constantly scanned by the wavelength variable filter 18, and each optical frequency information is extracted one by one. The next communication code detector 20 detects the destination code from the intensity modulated signal superimposed on the header of the packet, and if there is a code addressed to itself (addressed to the subscriber B), detects it in the channel control circuit 22. Inform

The channel control circuit 22 includes the selective receiving system 14
Of the selected photodetectors 16A, 16B,... The channel control circuit 22 manages an optical frequency having information addressed to itself.

One of the receivers selected from the selected light receivers 16A, 16B,... Takes out the designated optical frequency information and reproduces the transmission information. FIG. 5 is a diagram showing another configuration example of the receiving unit of the subscriber. In this embodiment, by assigning an optical frequency to each of a pair of subscribers related to a combination of transmission and reception among a plurality of subscribers, simple channel selection becomes possible without using a transmission destination code.
Specifically, it is as follows.

For example, between subscribers A and B, subscribers A and
Optical frequency f between C_AB, F _ACIs assigned
(F_AB≠ f_AC). From subscriber A on the transmitting side to subscriber B,
When sending signals to C and D, the part to be sent to subscriber B is optical.
Frequency f_AB, The part to be sent to the subscriber C is the optical frequency f_AC, Join
The part sent to the person D is the optical frequency f_ADBecomes

Now, consider the case where the subscriber B receives.
Subscriber B has optical frequency f_AB, F_CB, F _DBReceiving the light signal of
These optical signals are branched by the optical branching circuit 10 of FIG.
The data is supplied to the monitor 12 and the selective receiver 14. 5 of FIG.
The configuration of the receiving unit is different from that of the receiving unit in FIG.
2 is characterized in that it has a detector 24.

In the monitor system 12, the optical frequency is constantly scanned by the wavelength variable filter 18, and the optical frequency information is taken out one by one. The next detector 24 detects the signal power at the optical frequency addressed to itself by the channel control circuit 22.
Inform

The channel control circuit 22 instructs the selected receiver on the optical frequency to be selected. The channel control circuit 22 manages an optical frequency having information addressed to itself. According to this embodiment, since optical frequencies are assigned to each pair of subscribers related to the combination of transmission and reception, simple channel selection is possible without superimposing a transmission destination code as in the previous embodiment. Become. Further, the configuration of the detector 24 in the monitor system 12 in FIG. 5 can be simplified as compared with the configuration of the communication code detector 20 in the monitor system 12 in FIG.

[0031]

As described above, according to the present invention,
There is an effect that it is possible to provide a simple channel selection method in optical frequency division multiplex transmission.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of a network to which the present invention can be applied.

FIG. 2 is a diagram illustrating a configuration example of a transmission unit of a subscriber.

FIG. 3 is a diagram illustrating an example of a packet of transmission information.

FIG. 4 is a diagram illustrating a configuration example of a receiving unit of a subscriber.

FIG. 5 is a diagram illustrating another configuration example of the receiving unit of the subscriber.

[Explanation of symbols]

 A, B, C, D Subscriber RT Remote terminal 4 Laser diode 6 Optical modulator 10 Optical branch circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H04B 10/00 H04J 14/00

Claims (5)

(57) [Claims] 1. A plurality of subscribers (A, B, C, D,...) Having at least one of an optical transmitting function and an optical receiving function are connected by an optical fiber transmission line, and different frequencies are transmitted to the transmitting side subscribers. In the optical frequency division multiplexing transmission system in which the optical carrier is allocated, the transmitting side subscriber (A) modulates the angle of the optical carrier according to the transmission information and uses the transmission destination code for designating the destination subscriber. A channel selection method comprising: modulating a signal; and a receiving-side subscriber (B) discriminating the transmitting-side subscriber based on the destination code and reproducing desired transmission information. 2. The channel selection method according to claim 1, wherein the transmission information is subjected to packet processing, and the intensity modulation by the destination code is performed on a header portion of the packet. 3. The channel selection method according to claim 2, wherein a data portion of the packet is intensity-modulated by a scramble signal. 4. The channel selection method according to claim 1, wherein the transmission information is subjected to packet processing, and the intensity modulation by the destination code is performed on a header part and a data part of the packet. 5. An optical frequency division multiplex transmission system in which a plurality of subscribers (A, B, C, D,...) Having at least one of an optical transmission function and an optical reception function are connected by an optical fiber transmission line. An optical frequency is assigned to the pair of subscribers relating to the combination of transmission and reception, and the transmitting side subscriber (A) modulates the optical carrier of the assigned optical frequency with transmission information, and the receiving side subscriber (B) In the first aspect, a channel selection method is characterized in that a transmission side subscriber is determined by scanning a reception frequency and desired transmission information is reproduced.