JP3275213B2 - Service Slot Assignment Scheme for Optical Bidirectional Ring Transmission System - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a BLSR (Bidirectio
nal Line Switched Ring): Regarding the service slot allocation method in the optical two-way ring transmission method, the service slot allocation in the optical two-way ring transmission method enables the reduction of the circuit scale and the improvement of the reliability at the time of loopback. It is related to the allocation method.

The BLSR forms a ring-shaped transmission line using an optical fiber, and transmits a large amount of information while inserting / separating (Add / Drop) signals at a plurality of nodes provided on the ring. It is standardized by SONET in the United States.

[0003] In the BLSR, it is required that the required circuit scale be small and the reliability at the time of return be high when the return is performed due to a failure in an optical transmission line or the like.

[0004]

2. Description of the Related Art FIG. 5 shows an example of a conventional two-fiber BLSR.
Shown, 1_1,1_2,1_3,1 _Four Are optical
Counterclockwise optical transmission line consisting of fiber, 2_1,2_2,2_3,2_Four Is
Each is a clockwise optical transmission line made of an optical fiber.
3_1,3_2,3_3,3_Four Are nodes, each of which is an optical transmission
Relay the signal transmitted through the
Insertion of the dependent signal_,ADM for separation (Add / Drop
 Multiplexer) device.

In FIG. 5, a solid line indicates a time slot (service slot) of a service (working) line,
A path of a time slot (protection slot) of a protection (backup) line at the time of signal transmission is shown, and a broken line indicates a path of a protection slot at the time of termination. In each ADM device, S indicates a service slot to be relayed / transmitted, and a tributary (subordinate) signal is input / output to / from the service slot. PT indicates a protection slot relayed and transmitted at the time of termination. T indicates a tributary signal input / output by inserting and separating time slots.

In the ADM apparatus, in order to relay / transmit a signal and insert / separate a tributary signal, a TS is used.
An A (Time Slot Assign) circuit is required, and a TSI (Time Slot Interleave) circuit is used to relay and transmit signals, insert and separate tributary signals, and to exchange time slots for passing signals. is necessary.

In the two-fiber BLSR shown in FIG. 5, 48-channel low-order group signals (OC-1 signal: 50
MHz-high-order group of signals (OC-48 signal: 2.
In the case of applying 4 GHz), only 24 channels of 1 to 24 channels are used in the clockwise and counterclockwise directions as service slots at normal times, and the remaining 24 channels of 25 to 48 channels are free as protection slots.

[0008] Now, in the figure, the optical transmission path 2 _3, as shown by A
If the disconnection occurs, clockwise service slot (1~24CH), in ADM device 3 _4, through the PT as shown by the dashed line, it is inserted into the left-handed protection slot (25~48CH) ADM in Device 3 _1,
3 ₂ is transmitted through, the ADM device 3 _3, through the PT as shown by one-dot chain line, by being inserted into clockwise service slot (1～24CH), folded (loopback) is performed.

Therefore, in the ADM devices 3 _{3 and} 3 ₄ ,
While relaying the time slot of 24CH, inserting and separating the tributary signal, the time slot of the folded signal is changed from 1 to 24CH to 25 to 48C.
It is necessary to exchange H for 25-48CH to 1-24CH. Two-fiber BLS shown in FIG.
In R, each ADM device has a function of a TSI circuit in order to execute such a function.

FIG. 6 schematically illustrates a conventional four-fiber BLSR, in which a clockwise transmission line and a counterclockwise transmission line have a 1 + 1 configuration including a service line and a protection line, respectively. shows, ₁₁ 1, 11 _2,
11 _3, 11 ₄ are optical transmission lines forming a left-handed service line, 12 _1, 12 _2, 12 _3, 12 ₄ are optical transmission lines forming a right-handed service line, 13 _1, 13 _2, 13 _{3 ,} 13 ₄ optical transmission path to form a protection line counterclockwise, 1
4 _1, 14 _2, 14 _3, 14 ₄ are optical transmission lines forming a clockwise protection line. 15 _1, 15 _2, 15 _3, 15
Reference numerals ₄ denote nodes, each of which relays a signal transmitted through an optical transmission line and inserts / demultiplexes a tributary (subordinate) signal _, and an ADM (Add / Drop Multiplexer).
It consists of equipment.

In a normal state, the time slots (1 to 48 CH) of all the OC-48 channels are transmitted from the transmitting ADM device to the clockwise service line and the protection line, respectively, and the receiving ADM device is transmitted. , One of the lines is selected and received. Likewise
Also on the counterclockwise service line and protection line,
The transmitting side transmits time slots (1 to 48 CH) of all the channels of the OC-48, and the receiving side selects and receives any one of the lines. By performing such signal transmission and reception in each section, an optical bidirectional ring transmission path is formed.

FIGS. 7A and 7B are diagrams for explaining the control at the time of failure in the 4-fiber BLSR. FIG. 7A shows an example of the control of the 1 + 1 line switch, and FIG. 7B shows an example of the return control. . In the figure, reference numeral 16 denotes a line switching switch.

Now, in any section, the signal quality
If the drop occurs, the receiving ADM device
By switching from the current line to another line
Thus, signal quality can be restored. FIG. 7 (a)
In the example, the ADM device 15 _Two And ADM device 15_Three When
, The switch 16 is controlled on the receiving side.
Indicates that the line is to be switched.
ing.

If the signal quality cannot be recovered even by controlling the line switching, it can be remedied by excluding the faulty section and performing loopback. FIG.
In the example of (b), ADM in device 15 _4, to insert the service line 12 ₄ clockwise counterclockwise to the protection line 13 _4, counterclockwise service lines 11 ₄
Is inserted a clockwise protection line 14 _4, in other ADM device 15 _3, likewise clockwise and counterclockwise service lines, by inserting counterclockwise and clockwise protection lines, it is folded Once formed, the section excluding the fault location is rescued.

In the case of the four-fiber BLSR, the switching of the line switch or the loopback control does not cause the exchange of the time slot in the transmission line.
The DM device does not require a TSI circuit,
It can be configured by an SA circuit.

[0016]

In the two-fiber BLSR, it is necessary to switch the time slot of the passing signal from the service slot side to the protection slot side when performing the return. However, there is a problem in that a TSI circuit must be provided just to replace the time slots, and it is unavoidable to be expensive.

In the four-fiber BLSR, it is not necessary to change the time slot of the passing signal when performing the return control. However, even when the line is switched or the return control is performed. , To switch all lines, signal interruption (Hi
t) occurs.

The present invention is intended to solve such a problem of the prior art. In the two-fiber BLSR, a TSI circuit is not required to replace a time slot at the time of turning back, and the four-fiber BLSR does not require a TSI circuit. It is another object of the present invention to provide a service slot allocation method in an optical bidirectional ring transmission system in which the number of channels that cause a momentary signal interruption is small.

[0019]

Means for Solving the Problems (1) The service slot allocation method in the optical bidirectional ring transmission method according to the present invention is a method for relaying / transmitting a passing signal and inserting / separating a tributary signal from / to the passing signal. ADM device 3 _1,
3 _2, 3 _3, ... and two optical transmission lines 1 _1, 1 _2, 1 _3, ..., 2 _1, 2
_In a two-fiber optical bidirectional ring transmission system for transmitting signals of a plurality of channels by alternately connecting bidirectional lines consisting of _2, 2, ₃ ,. One channel and the other channel obtained by dividing all the channels into two are allocated to a service slot and a protection slot, respectively, and the protection slot is transmitted in an empty state. In the other optical transmission line, one channel and the other channel are transmitted. Each is assigned to a protection slot and a service slot, and the protection slot is transmitted as an empty state.In the folded state, the service slot of one and / or the other optical transmission line is inserted into the protection slot of the other and / or one of the optical transmission lines. To be transmitted.

(2) Optical bidirectional ring transmission system of the present invention
The service slot allocation method in
Relay / transmission and tributary signal for passing signal
ADM devices 15 for insertion and separation of data_1,Fifteen_2,Fifteen
_3,, And two optical transmission paths 11_1,11_2,11_3,…, 12
_1,12_2,12_3,… And 13_1,13_2,13_3,…, 14 _1,
14_2,14_3,Alternately with two bidirectional lines consisting of
4-fiber connected in a ring to transmit signals of multiple channels
In the fiber optical two-way ring transmission system,
Is a two-way optical transmission line that forms one line.
To divide all channels into two, one channel and the other channel
Service slot and protection slot, respectively.
Lots and protection slots
Are transmitted in an empty state to form the other line
One channel and the other channel
And protection slot and service slot respectively.
And a protection slot
It transmits as an empty state, and one side and
Or change the service slot on the other line to the other
And / or protection slot on one line
It is inserted into the packet and transmitted.

[0021]

[Function] (1) Two-fiber optical bidirectional ring transmission system
A plurality of ADM devices 3_1,3 _2,3_3,... and two light transmissions
Route 1_1,1_2,1_3,…, 2_1,2_2,2_3,... two-way la
Are connected alternately in a ring shape to
ADM device 3_1,3_2,3_3,To ...
Relay and transmission of passing signals, and
Inserts and separates a reputable signal.

In this case, in the normal state, one channel and the other channel obtained by dividing all the channels into two are assigned to a service slot and a protection slot in one optical transmission line, and the protection slot is transmitted in an empty state. In the other optical transmission line, one channel and the other channel are allocated to a protection slot and a service slot, respectively, and the protection slot is transmitted in an empty state.

In the return state, in the ADM apparatus that performs the return, the service slot of one and / or the other optical transmission line is inserted into the protection slot of the other and / or one of the optical transmission lines and transmitted.

According to the present invention, there is no need to exchange time slots at the time of loopback, so that a TSI circuit is not required, and therefore, the size of the apparatus can be reduced and the cost can be reduced.

(2) Four-fiber optical bidirectional ring transmission system
In this case, a plurality of ADM devices 15_1,Fifteen_2,Fifteen_3,…When,
Each two optical transmission lines 11_1,11_2,11_3,…, 12_1,12_2,
12 _3,… And 13_1,13_2,13_3,…, 14_1,14_2,1
4_3,… Two bidirectional lines alternately in a ring shape
To transmit signals on multiple channels and
ADM device 15_1,Fifteen_2,Fifteen_3,... in the passing signal
Relay / transmission and tributary signal
Perform insertion and separation.

At this time, in the normal state, in the bidirectional optical transmission line forming one line, one channel and the other channel obtained by dividing all the channels into two are allocated to the service slot and the protection slot, respectively, In the two-way optical transmission line forming the other line, the one channel and the other channel are allocated to the protection slot and the service slot, respectively, and the protection slot is transmitted in the empty state.

In the loopback state, the ADM apparatus that performs loopback inserts a service slot in one and / or the other line into a protection slot in the other and / or one of the lines and transmits.

According to the present invention, at the time of loopback, there is no change in the connection of the service slot inserted / separated in the ADM apparatus.

[0029]

FIG. 1 shows an embodiment of the present invention, in which a two-fiber BLSR is used, and the same elements as those in FIG. 5 are indicated by the same reference numerals. The case of FIG. 1 is different from the case of FIG. 5 in that the channel assignment between the service slot and the protection slot is reversed in one line, for example, the clockwise optical transmission line.

In the embodiment shown in FIG. 1, for example, in the counterclockwise line, the first half of channels 1 to 24 are assigned to the service slot, and the second half of channels 25 to 48 are assigned to the protection slot.
When H is assigned, the second half 25 to 48 are assigned to the service slot in the clockwise line, and the first half 1 to 24 are assigned to the protection slot.

Thus, according to the embodiment shown in FIG.
Since it is not necessary to exchange time slots at the time of loopback, it is not necessary to have a TSI circuit for loopback.

As described above, according to the present invention, in one line, one channel and the other channel obtained by dividing all the channels into two are allocated to the service slot and the protection slot, respectively, and the protection slot is transmitted in an empty state. At the same time, on the other line, these are allocated to a protection slot and a service slot, respectively, and the protection slot is transmitted in an empty state. In this case, the method of dividing all the channels into two is arbitrary.

FIG. 2 shows another embodiment of the present invention.
FIG. 6 shows the case of a 4-fiber BLSR.
The same items are indicated by the same numbers. The place of the present invention
Optical transmission line 11_1,11_2,11_3,11_Four And 12_1,12
_2,12_3,12_Four And a line 1 is formed by the optical transmission line
13_1,13_2,13_3,13_Four And 14_1,14_2,14_3,14
_Four A line 2 is thus formed.

At normal times, the optical transmission lines 11 _1, 11 _2,
11 _3, 11 ₄ , the first half of 1 to 24 channels are allocated as the counterclockwise service slot of line 1, and the second half of 25 to 4
With the idle state 8CH as protection slot, the optical transmission path ₁₂ 1, 12 _2, 12 _3, 12 _4, of the first half as a clockwise service slot line 1 1 to 24
CHs are allocated, and the second half of CHs 25 to 48 are set as protection slots and set in an empty state.

The optical transmission line 13_1,13_2,13_3,13_Four 
In the second half of the line,
Allocate 25-48CH, and allocate the first 1-24CH
While leaving it empty as a protection slot,
Transmission line 14_1,14_2,14_3,14 _Four To the right of line 2
25-48CH in the latter half as service slot
Guess, the first half 1-24CH is a protection slot
To make it empty.

As described above, in the present invention, all the channels are set to 2 in the left-handed and right-handed optical transmission lines forming the line 1.
One of the divided channels is assigned as a service slot, the other channel is left empty as a protection slot, and the other of the two channels is divided into two in the left-handed and right-handed optical transmission lines that form line 2. Allocated as a slot, and one of the channels is set as a free slot as a protection slot. In this case, the method of dividing all the channels into two is arbitrary.

[0037] Figure 3, in the embodiment of FIG. 2, there is shown the passing signal and tributary signal nodes illustrate the case of ADM device 15 ₁ in FIG. 2 as nodes.

At normal times, as shown in FIG.
In DM 15 _1, for each passage signal of the left-handed and right-handed line 1, respectively timeslot 1
~ 24CH are inserted / separated and line 2
The time slots 25 to 48CH are inserted / separated for each of the counterclockwise and clockwise passing signals.

[0039] Figure 4, in the embodiment of FIG. 2, there is described a folded control, it illustrates the case of ADM device 15 ₁ in FIG. 2 as nodes.

As shown in FIG. 4, for example, the ADM device 15
_{If a} failure occurs on the left side of ₁ and loopback is performed, clockwise service slots 25 to 48CH of line 2 are inserted into empty slots on the left side of line 1 to
H is transmitted, the clockwise service slots 1 to 24CH of the line 1 are inserted into the counterclockwise empty slots of the line 2, and the channels 1 to 48 are transmitted, so that the clockwise service slots are turned counterclockwise. To

[0041] At this time, the service slot 1~24CH line 1 for folding, the line 2 service slots 25～48CH, but produces a signal interruption by switching the connection, inserting and separating the ADM device 15 ₁ Since there is no change in the connection between the service slots 1 to 24CH and 25 to 48CH, no signal interruption occurs.

[0042]

As described above, according to the present invention, 2
Conventionally, in the case of the fiber BLSR, a TSI circuit is required to switch the time slot of the passing signal at the time of turning back. However, in the present invention, the switching of the time slot of the passing signal is not required at the time of turning back, so an expensive TSI circuit Becomes unnecessary.

In the case of the four-fiber BLSR, it is not necessary to change the time slot of the passing signal when performing the return control.
While instantaneous signal interruption occurred in all channels, in the present invention,
Signal instantaneous interruption does not occur for signals inserted / separated at the node, so that communication quality can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of the present invention.

FIG. 2 is a diagram showing another embodiment of the present invention.

FIG. 3 is a diagram showing a passing signal and a tributary signal of a node in the embodiment of FIG. 2;

FIG. 4 is a diagram for explaining return control in the embodiment of FIG. 2;

FIG. 5 is a diagram illustrating a conventional two-fiber BLSR.

FIG. 6 is a diagram illustrating an outline of a conventional four-fiber BLSR.

FIG. 7 is a diagram illustrating control at the time of a failure in the 4-fiber BLSR.

[Explanation of symbols]

1 _, 1 _2, 1 ₃ … Optical transmission path 2 _1, 2 _2, 2 ₃ … Optical transmission path 3 _1, 3 _2, 3 ₃ … ADM device 11 _1, 11 _2, 11 ₃ … Optical transmission Paths 12 _1, 12 _2, 12 ₃ ... Optical transmission paths 13 _1, 13 _2, 13 ₃ ... Optical transmission paths 14 _1, 14 _2, 14 ₃ ... Optical transmission paths 15 _1, 15 _2, 15 ₃ ... ADM equipment

────────────────────────────────────────────────── (5) References JP-A-5-268234 (JP, A) Tson-Ho Wu, Fiber Network Service Survivability, United States, Art Tech House, Inc., p. 123-144 (58) Field surveyed (Int.Cl. ⁷ , DB name) H04L 12/437

Claims (1)

(57) [Claims] A plurality of As for relaying / transmitting a passing signal and inserting / separating a tributary signal from / to the passing signal.
In a four-fiber optical bidirectional ring transmission system in which a DM device and two bidirectional lines each composed of two optical transmission lines are alternately connected in a ring shape to transmit signals of a plurality of channels, In a bidirectional optical transmission line forming one line, one channel and the other channel obtained by dividing all the channels into two are assigned to a service slot and a protection slot, respectively, and the protection slot is transmitted in an empty state. In the bidirectional optical transmission line forming the line, the one channel and the other channel are respectively allocated to a protection slot and a service slot, and the protection slot is transmitted as an empty state. Each service slot on the other line Input time slots to the protection slots in the other or one of the lines
A service slot allocation method in an optical two-way ring transmission method, wherein the transmission is performed without being replaced .