JP3031290B2 - Delay measurement method in optical transmission system with PDS configuration - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical subscriber system and, more particularly, to a PDS (Passive Double).
The present invention relates to a method for measuring a delay time when a subscriber unit joins in an optical transmission system having a passive (star) configuration.

[0002]

2. Description of the Related Art An example of the configuration of a conventional PDS optical transmission system shown in FIG. 3 is shown. Referring to FIG. 3, the optical output from the optical burst transmission unit 1-1 of the center-side device 1 is split 1: n by an optical splitter / coupler (hereinafter, referred to as a “star coupler”) 2, and n light beams are output. , 4n.

The optical outputs from the optical network units 41,..., 4n are combined by the star coupler 3 and input to the optical burst receiving unit 1-2 of the center unit 1.

When a certain optical subscriber unit newly subscribes,
The signal output from the optical burst transmission section 1-1 of the center-side device 1 is added to a subscription slot of a downlink signal, an example of a frame format shown in FIG. To reach.

Conversely, a response signal from the optical subscriber unit is added to an uplink signal subscribing slot whose frame format is shown in FIG. -2, the delay measurement unit 1-
At 7, the delay time is measured.

The data of the delay time is input to a timing generator 1-8, which generates a response timing of an optical subscriber unit to be added, and then is input to an optical burst transmitter 1-1 to receive an optical subscriber unit 41. , ..., 4n.

When a new optical subscriber unit subscribes, as shown in FIG. 4, a subscribing slot is provided in each of the downstream frame format and the upstream frame format. Since the optical burst data to which the newly subscribed optical subscriber unit responds for the first time is not subjected to the delay control, the insertion position of the uplink frame format is undefined. For this reason,
It is necessary to secure a data length corresponding to the delay time in consideration of the distance between the center device side and the subscriber side where the installation of the optical subscriber device is allowed.

Next, FIGS. 5 and 6 show a cell-based ATM (Ashchronous Transf.).
er Mode (asynchronous transfer mode) is a conventional example in a transmission system.

The prior art showing the system configuration in FIG.
This is a method in which a vacant (unused) TS (time slot) is used when a subscriber unit subscribes.

The newly installed subscriber device (# 1)
After receiving the signal by the downlink signal receiving circuit 201,
(Time slot) The identifier detection circuit 204 detects an empty time slot.

When an empty time slot is detected, the path of the switch 203 is switched to switch the phase adjustment signal generation circuit 21.
The signal from 0 is transmitted from the upstream signal transmission circuit 202.

At this time, the center device transmits this signal
The signal is received by the upstream signal receiving circuit 101. Normally, the path of the switch 103 on the center side is
Is set to

The upstream communication signal processing circuit 106 recognizes that this signal is a signal for phase adjustment, switches the path of the switch 103, and makes the signal of this time slot go to the phase delay measuring circuit 108. To

The phase delay is measured by the phase delay measuring circuit 108, and the result is written to the phase delay amount inserting circuit 109.
The downlink signal transmission circuit 102 transmits the signal.

At this time, the phase delay amount measurement control circuit 112
Sends to the subscriber identifier insertion circuit 110, the TS identifier insertion circuit 111, and the phase adjustment signal request signal insertion circuit 117, the identification code of the newly added subscriber unit # 1, the phase correction time, and the phase adjustment signal. It instructs to write the transmission request signal to the signal of the time slot of downlink TS # 1.

At the same time, the center-side apparatus operates by switching the switch 103 so as to send a reception signal to the phase delay measurement circuit 108 for TS # 1 in the reception time slot.

The subscriber unit # 1 receives this signal, and the time slot identifier, the subscriber identifier detection circuit 205, and the phase adjustment signal request signal detection circuit 217 receive the time slot and the subscriber, respectively. , The phase adjustment signal request signal is identified, the phase delay amount D1 to be set by the subscriber is set by the phase delay amount setting circuit 209, and the switch 2
03, the transmission of the signal from the upstream communication signal processing circuit 207 is started.

FIG. 6 is a timing chart for explaining the prior art in which the transmission processing timing and the reception processing timing in the center-side device are shared to reduce the number of timing processing circuits.

Referring to FIG. 6, a description will be given of a case where the center side apparatus and the subscriber side apparatus are set to the shortest distance. The TS transmission timing in the downlink transmission circuit from the center side apparatus is 1. Each piece of TS information that is output earlier at this timing arrives at the subscriber device at a timing of 2 without delay.

At this time, after the end of TS1 is received, it is transmitted from the uplink transmission circuit after an additional delay time Dmin (Dmin = 1TS (27 cells)). This operation timing is 5.

Further, the TS1 signal output earlier at the transmission timing arrives at the center device at the timing of 8, so that the operation timing of the reception circuit of the center device can be shared by the transmission / reception circuit and the reception side TS number can be transmitted to the transmission side. What is necessary is just to shift by 2TS from the TS number.

Next, the case where the center-side device and the subscriber-side device are installed at the maximum distance will be described. Also in this case, the TS timing in the center-side downlink transmission circuit is set to 1.

Each piece of TS information transmitted at this timing arrives at the subscriber device at timing 4 with a delay of the maximum delay amount / 2 (13 cells).

Further, after receiving the end of TS2, after an additional delay time Dmax (Dmax = 1 cell), it is transmitted from the uplink transmission circuit.

The TS transmitted at the transmission timing of 7
The two signals are further delayed by the maximum delay amount / 2 (13 cells) on the line and arrive at the center-side device at the timing of 8. Also in this case, the operation timing of the receiving circuit of the center side apparatus can be shared by the transmitting / receiving circuit, and the receiving side TS number is
What is necessary is just to shift 2TS from S number.

Further, the case where the center-side device and the subscriber-side device are connected at an arbitrary distance and the TS 16 is allocated will be described.
The S timing is 1.

Each piece of TS information transmitted at this timing arrives at the subscriber device at timing 3 with a delay of 10 cells.

Further, after the end of TS16 is received, after an additional delay time Dx (Dx = 7 cells), it is transmitted from the uplink transmission circuit.

The TS transmitted at the transmission timing of 6
The 16 signals arrive at the center device at a timing of 8 after being further delayed by 10 cells on the line. Also in this case, the operation timing of the receiving circuit of the center-side device can be shared by the transmitting and receiving circuits, and the receiving-side TS number may be shifted by 2 TS from the transmitting-side TS number.

In the prior art relating to the cell-based ATM transmission system described above, the maximum transmission delay time Dmax is set to 26 cells, and a measurement cell (P: 1 cell) is added.
Since seven cells are defined as one information unit (TS), delay adjustment using vacant time slots is possible.

However, in the system configuration to which the present invention is applied, the minimum information unit is different from the conventional cell-based ATM system, and is intended for an information amount of about 64 kbps × N (N is an integer). However, as described above, a time slot for subscription is separately secured as shown in FIG. 5 and a time slot length in consideration of the maximum delay time is required.

[0032]

As described above, the above prior art has the following problems.

(1) When an optical subscriber unit newly subscribes, it is necessary to provide a subscribing slot so that initial response data not subjected to delay control does not collide with service data under subscription. In consideration of the maximum allowable installation distance between the center-side device and the optical subscriber unit, it is necessary to secure a data length that can absorb the corresponding delay time.

(2) Also, as in the cell-based ATM transmission system, one time slot (TS) is set with a data length corresponding to the maximum delay amount. In this case, any of the vacant time slots is set. However, the delay control is possible, but this method is used in the present invention for 1TS.
The system cannot cope with a system configuration in which the information amount is several times as large as 64 kbps, and it is necessary to secure unused time slots for subscription.

For this reason, when the maximum allowable installation distance between the devices is large, the length of the joining slot becomes long, and the data length usable for the operation service in the frame format becomes short, so that the line accommodation efficiency becomes poor. was there.

Therefore, the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method of setting a joining slot in a frame configuration by a value of an installation distance between a center unit and an optical subscriber unit. It is an object of the present invention to provide an optical subscriber system in which the length of a subscription slot is shortened by dividing and using, and the accommodation efficiency of a service line used for operation is further improved.

[0037]

In order to achieve the above-mentioned object, the present invention is directed to a center-side device and a plurality of (N) optical subscriber units each having two star couplers in each of the upstream and downstream directions. : In the optical transmission system having a PDS (passive double star) configuration connected to N, the center-side device receives an optical burst from a star coupler in an upstream direction, and a signal from the optical burst receiver. , An offset value detecting section for detecting an offset value, a signal from the offset value detecting section, a fine delay adjusting section for performing fine delay adjustment, and a signal from the fine delay adjusting section, A timing generator for generating a response timing of the optical network unit, and a signal from the timing generator, and a burst signal to each optical subscriber unit via a star coupler in a down direction. An optical burst transmitting unit, which outputs an optical burst signal, wherein the optical subscriber unit inputs an optical burst signal output by the center-side device via a downstream star coupler; and A light-receiving power calculation unit that inputs a signal and calculates the installation distance from the optical power, and an offset control unit that inputs a signal from the light-receiving power calculation unit and determines the insertion timing of a joining slot in an uplink frame format by offset control. A timing generation unit that inputs a signal from the offset control unit, an optical burst transmission unit that receives a signal from the timing generation unit, and outputs optical burst data to a center device via an upstream star coupler; It is characterized by having.

[0038]

Embodiments of the present invention will be described below. In a preferred embodiment of the present invention, the center-side device (1 in FIG. 1) includes an optical burst receiving unit (1 in FIG. 1) for inputting a signal from a star coupler in an upstream direction.
-2), and an offset value detection unit (1--1 in FIG. 1) which receives a signal from the optical burst reception unit and detects a response frame.
3), a signal from the offset value detection unit is input, and a delay fine adjustment unit (1-4 in FIG. 1) for performing fine adjustment of the delay; Timing generator (1-5 in FIG. 1) for generating a response timing of the device
And an optical burst transmission unit (1-1 in FIG. 1) for inputting a signal from the timing generation unit and outputting a burst signal to each optical subscriber unit via a downstream star coupler. .

The optical subscriber unit (4-1 to 4- in FIG. 1)
n) is an optical burst receiving unit (4-1 in FIG. 1) for inputting an optical burst signal output from the center-side device via a downstream star coupler (2 in FIG. 1), and a signal from the optical burst receiving unit. A light receiving power calculating unit (4-2 in FIG. 1) for inputting a signal and calculating an installation distance from the optical power, and inputting a signal from the light receiving power calculating unit to offset the insertion timing of a joining slot in an uplink frame format. An offset control unit (4-5 in FIG. 1) for controlling, and a timing generation unit (4--5 in FIG. 1) for inputting a signal from the offset control unit
4), and an optical burst transmission unit (4-3 in FIG. 1) that receives a signal from the timing generation unit and outputs optical burst data to the center-side device via an upstream star coupler.

In the embodiment of the present invention, when a new optical subscriber unit joins, in the optical subscriber unit, the timing generation unit (4-4 in FIG. 1) includes an offset control unit (4-4 in FIG. 1). According to the offset control data (correction counter value) calculated in 4-5), the response frame to the center-side device is delayed by one frame, and corresponds to the corresponding offset control data from the timing at which the next joining slot starts. At a timing earlier by the data length,
Response data is set, and an offset value based on the result of the offset control unit (4-5 in FIG. 1) is inserted into the response data.

In the embodiment of the present invention, the center unit transmits the uplink data received from the optical subscriber unit to the next subscription slot if no response data exists in the first subscription slot. After recognizing existing response data and performing delay correction corresponding to the offset value based on the offset value inserted in the received response data, fine-adjustment is performed by the delay fine-adjustment unit, The generation unit receives a signal from the delay fine adjustment unit and generates a response timing of each subscriber device.

In the embodiment of the present invention, when a new optical subscriber unit subscribes, if a response is made on the transmission side, the subscription slot corresponds to the delay time required for fine delay adjustment. By using only the time slot length, for the distance corresponding to the coarse adjustment, the value calculated from the received optical power is converted as a delay time by the offset control unit, and transmitted to the center side as response data, so that the The setting is omitted.

For this reason, only the data length corresponding to the uncertain delay time whose distance conversion value fluctuates due to the system margin of the optical power needs to be secured as the joining slot, so that the line use efficiency can be improved. Becomes

[0044]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention;

FIG. 1 is a block diagram showing a main part of an embodiment of the present invention. In FIG. 1, an optical transmission system having a PDS configuration in which one center-side device 1 and N optical subscriber units 41 to 4n are connected in a 1: N manner by two star couplers 2 and 3 in the upstream and downstream directions, respectively. Doing

An optical burst receiving unit 1-2 for inputting a signal from the star coupler 3 in the upstream direction is input to the center-side device 1.
And a response frame detecting unit 1-33 for inputting a signal from the optical burst receiving unit 1-2 and detecting a response frame, and a fine delay for inputting a signal from the response frame detecting unit 1-3 and performing fine delay adjustment. A timing generation unit 1-5 that receives signals from the adjustment unit 1-4 and the delay fine adjustment unit 1-4 and generates a response timing of each subscriber device;
5 has an optical burst transmitting unit 1-1 for inputting a signal and outputting a burst signal to each of the optical subscriber units 41 to 4n via the downstream star coupler 2.

The optical subscriber units 41 to 4n are provided with an optical burst receiving unit 4-1 for inputting an optical burst signal output from the center unit 1 via the downstream star coupler 2, and an optical burst receiving unit 4-1. Power calculation unit 4-2 for inputting a signal from the optical power and calculating the installation distance from the optical power, and inputting a signal from the light reception power calculation unit 4-2 for offset control of the insertion timing of the joining slot in the uplink frame format. And a timing generator 4-4 for inputting a signal from the offset controller 4-5.
And an optical burst transmission unit 4-3 that receives a signal from the timing generation unit 4-4 and outputs optical burst data to the center-side device 1 via the upstream star coupler 3.

Next, the operation of the optical subscriber unit having the above-described configuration according to the present embodiment will be described. FIG. 2 is a diagram illustrating an example of a frame format for describing features of the present embodiment.

The optical subscriber unit 4m (m: natural number, 1 ≦ m ≧
In the example of n), when m = 1 newly joins, the center side apparatus 1 transmits a join command using the join slot in the downlink signal shown in FIG. , And the corresponding optical subscriber unit 41
Are received by the optical burst receiving section 4-1.

The received command is transmitted to the light-receiving power calculation unit 4-
2, the distance between the installation of the own device and the center-side device 1 is estimated from the light receiving power, and the offset control unit 4-
5 is input.

Now, the distance calculated from the optical power is specifically 1
Suppose it was 2 km. When a system margin due to a coupling loss in the optical transmission line or a loss due to fiber deterioration is taken into account, an error naturally occurs in the calculation result. However, when an error in distance conversion due to the system margin is considered to be, for example, 2 km, 10 km is equal to 10 km. It is a certain value.

The offset control section 4-5 calculates this reliable value and sends the corresponding correction counter value to the timing generation section 4-4.

In the timing generation section 4-4, according to the correction counter value indicated by the offset control section 4-5,
The response frame is delayed by one frame, and the response data is set at a timing earlier by the corresponding correction counter value (that is, before the data length corresponding to the offset value) than the timing at which the next addition slot starts (see FIG. 2 ( b)).

As a result, the timing corrected by only 10 km is transmitted to the center device 1, and the distance (2 km) where the uncertain element remains is transmitted to the center device 1 as a delay time as it is. become.

On the other hand, in the center-side device 1, the response data is received by the optical burst receiving unit 1-2 via the upstream star coupler 3, and the response frame detecting unit 1--1.
Enter 3

If there is no response data in the first subscription slot, response data existing in the next subscription slot is recognized (see FIG. 2C).

In the center device 1, in the case of the conventional method, 1
Although the response data was received at a timing delayed by an amount corresponding to the distance of 2 km (see ☆ in FIG. 2C), in the present embodiment, the subscriber side device transmits 10 km earlier. Therefore, this delay has been cut.

In the received response data, the 10 km offset control data (correction counter value) based on the result of the offset control unit 4-5 is inserted in the timing generation unit 4-4 of the subscriber unit. (Figure 2
(B), FIG. 2 (c)), in the center-side device 1, after performing the delay correction of 10 km by the correction counter detected by the offset value detection unit 1-3, the delay fine adjustment unit 1
-4, the response data is transmitted.

In the delay fine adjustment section 1-4, fine adjustment is performed in the same manner as in the conventional method, and then the delay time corresponding to 10km is corrected by the correction counter value and sent to the timing generation section 1-5. As a result, the timing generator 1-
At 5, a response timing for the optical subscriber unit 4-1 is generated.

As described above, the data length corresponding to the approximate distance is cut by the offset control, and only the data length necessary for the fine adjustment is used as the delay control, thereby making it possible to shorten the subscription slot.

[0061]

As described above, according to the present invention,
When a new optical subscriber unit joins, if a response is made on the transmitting side, only the time slot length corresponding to the delay time required for fine delay adjustment is used for the joining slot, and the distance corresponding to the coarse adjustment is used. For, the value calculated from the received optical power is converted as a delay time by the offset control unit,
By transmitting the response data to the center, the setting to the subscription time slot can be omitted.

For this reason, according to the present invention, only the data length corresponding to the uncertain delay time in which the distance conversion value fluctuates due to the system margin of the optical power needs to be secured as the joining slot. The usage efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing a frame format according to an embodiment of the present invention.

FIG. 3 is a block diagram of a conventional optical communication device.

FIG. 4 is a diagram showing a frame format according to the related art.

FIG. 5 is a diagram showing a system configuration of a second conventional technique.

FIG. 6 is a timing chart for explaining the operation of the second conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Center apparatus 1-1, 4-3 Optical burst transmitting section 1-2, 4-1 Optical burst receiving section 1-3 Offset value detecting section 1-4 Fine delay adjusting section 1-5, 4-4 Timing generating section 1-7 Delay Measurement Unit 1-8 Timing Generation Unit 2, 3 Star Coupler 4-1 to n Optical Subscriber Unit 4-2 Light Receiving Power Calculation Unit 4-5 Offset Control Unit 101 Uplink Signal Receiving Circuit 102 Downlink Signal Transmitting Circuit 103 Switch (SW) 104 TS identifier detection circuit 105 Subscriber identifier detection circuit 106 Uplink communication signal processing circuit 107 Downlink communication signal processing circuit 108 Phase delay measurement circuit 109 Phase delay amount insertion circuit 110 Subscriber identifier insertion circuit 111 TS identifier insertion circuit 112 Phase delay amount measurement control circuit 117 Phase adjustment signal request signal insertion circuit 201 Up signal reception circuit 202 Down signal reception Circuit 203 Switch (SW) 204 TS identifier detection circuit 205 Subscriber identifier detection circuit 206 Downlink communication signal processing circuit 207 Uplink communication signal processing circuit 208 Phase delay amount identification circuit 209 Phase delay amount setting circuit 210 Phase adjustment signal generation circuit 211 Subscriber Identifier insertion circuit 212 TS identifier insertion circuit 217 Phase adjustment signal request signal detection circuit

Claims (4)

(57) [Claims] An optical system having a PDS (passive double star) configuration in which one center-side device and a plurality of (N) optical subscriber units are connected 1: N by two star couplers in each of an upstream direction and a downstream direction. In the transmission system, when a response is made on the optical subscriber unit side, for example, when a new optical subscriber unit joins, a time slot length corresponding to the delay time required for fine adjustment of delay is added to the addition slot. Used, the rough adjustment, the distance between the installation with the center device, the value calculated from the received optical power is converted as a delay time by the offset control unit, and transmitted to the center device as response data, An optical subscriber system. 2. A light having a PDS (passive double star) configuration in which one center-side device and a plurality (N) of optical subscriber units are connected 1: N by two star couplers in each of an upstream direction and a downstream direction. In the transmission system, the center-side device receives an optical burst signal from an upstream star coupler, receives an optical burst signal, receives the signal from the optical burst receiver, detects an offset value, and detects an offset value. A fine delay adjusting unit that receives a signal from the offset value detecting unit and performs fine delay adjustment; a timing generating unit that receives a signal from the fine delay adjusting unit and generates a response timing of each subscriber device; An optical burst transmitting unit that receives a signal from the optical subscriber unit and outputs a burst signal to each optical subscriber unit via a downstream star coupler. An optical burst receiving unit that inputs an optical burst signal output from the center-side device via a downstream star coupler; and inputs a signal from the optical burst receiving unit and calculates an installation distance from optical power. A light-receiving power calculation unit, an offset control unit that receives a signal from the light-receiving power calculation unit and determines the insertion timing of a joining slot in an uplink frame format by offset control, and a timing generation that inputs a signal from the offset control unit An optical subscriber system, comprising: a unit; and an optical burst transmitting unit that receives a signal from the timing generation unit and outputs optical burst data to a center device via an upstream star coupler. 3. When the optical subscriber unit newly joins, in the optical subscriber unit, the timing generation unit generates a response frame to the center unit according to the offset value calculated by the offset control unit. The response data is set at a timing earlier by the data length corresponding to the corresponding offset value than the timing at which the next subscription slot starts, and the response data includes an offset value based on the result of the offset control unit. 3. The optical subscriber system according to claim 2, wherein the optical subscriber system is inserted. 4. The center-side device transmits the response data present in the next subscription slot if no response data exists in the first subscription slot for the uplink data received from the optical subscriber device. After performing the delay correction corresponding to the offset value based on the offset value inserted in the response data that is recognized and received, after the fine adjustment is performed by the delay fine adjustment unit, the timing generation unit 3. The optical subscriber system according to claim 2, wherein a signal from the delay fine adjustment unit is input to generate a response timing of each subscriber device.