Optical communication system including replaceable electro-optic and opto-electric converters

1. Field of the Invention

The present invention relates to an optical communication system including electro-optic converters and opto-electric converters.

2. Description of the Related Art

Generally, an optical communication system is duplex to realize a protection system. That is, a working optical transmission line and a standby optical transmission line are provided for one channel. As a result, when the working optical transmission line fails, the working optical transmission line is switched to the standby optical transmission line, or vice versa.

In prior art duplex optical communication systems, optical cards each including at least one electro-optic converter or opto-electric converter are fixed to a motherboard. This will be explained later in detail.

As a result, when one electro-optic converter (or opto-electric converter) fails, the operation of the entire optical transmitting (or receiving) apparatus has to be stopped, so that the optical card including such a failed converter can be replaced with a new one. This deteriorates the efficiency of the maintenance of the duplex communication system.

It is an object of the present invention to provide an optical transmitting apparatus, an optical receiving apparatus and an optical communication system capable of improving the efficiency of the maintenance.

According to the present invention, in an optical transmitting or receiving apparatus of an optical communication system, a plurality of replaceable electro-optic converters or a plurality of replaceable opto-electric converters are provided in correspondence with optical transmission lines.

The present invention will be more clearly understood from the description set forth below, as compared with the prior art, with reference to the accompanying drawings, wherein:

FIG. 1 is a block circuit diagram illustrating a first prior art duplex optical communication system;

FIG. 2 is a perspective view illustrating the optical transmitting apparatus (the optical receiving apparatus) of FIG. 1 ;

FIG. 3 is a block circuit diagram illustrating a second prior art duplex optical communication system;

FIG. 4 is a perspective view illustrating the optical transmitting apparatus (the optical receiving apparatus) of FIG. 3 ;

FIG. 5 is a block circuit diagram illustrating a first embodiment of the duplex optical communication system according to the present invention;

FIG. 6 is a perspective view illustrating the optical transmitting apparatus (the optical receiving apparatus) of FIG. 5 ;

FIG. 7 is a block circuit diagram illustrating a second embodiment of the duplex optical communication system according to the present invention; and

FIG. 8 is a perspective view illustrating the optical transmitting apparatus (the optical receiving apparatus) of FIG. 7 .

Before the description of the preferred embodiments, prior art duplex optical communication systems will be explained with reference to FIGS. 1 , 2 , 3 and 4 .

In FIG. 1 , which illustrates a first prior art duplex optical communication system (see: JP-A-8-125636), an optical transmitting apparatus 1 and an optical receiving apparatus 2 are connected by n-channel working optical transmission lines 3 W- 1 , 3 W- 2 , . . . , 3 W-n and n-channel standby transmission lines 3 S- 1 , 3 S- 2 , . . . , 3 S-n made of optical fibers.

The optical transmitting apparatus 1 is constructed by 1-channel type branching units 11 - 1 , . . . , 11 -n, 1-channel type working optical transmitting cards 12 W- 1 , . . . , 12 W-n and 1-channel type standby optical transmitting cards 12 S- 1 , . . . , 12 S-n. In this case, the branching unit 11 -i (i=1, . . . , n) is connected to the working optical transmitting card 12 W-i and the standby optical transmitting card 12 S-i. Also, each of the optical transmitting cards 12 W- 1 , . . . , 12 W-n, 12 S- 1 , . . . , 12 S-n is constructed by a monitoring information adding unit 121 for adding monitoring information such as parity check bits and an electro-optic converter 122 .

On the other hand, the optical receiving apparatus 2 is constructed by 1-channel type working optical receiving cards 21 W- 1 , . . . , 21 W-n, 1-channel type standby optical receiving cards 21 S- 1 , . . . , 21 S-n, selectors 22 - 1 , . . . , 22 -n and a control unit 23 . In this case, the selector 22 -i (i=1, . . . , n) is connected to the working optical receiving card 21 W-i and the standby optical receiving card 21 S-i. Also, each of the optical receiving cards 21 W- 1 , . . . , 21 W-n, 21 S- 1 , . . . , 21 S-n is constructed by an opto-electric converter 211 and a transmission path monitoring unit 212 for monitoring the corresponding transmission line by detecting monitoring information thereon. Further, the control unit 23 receives output signals of the transmission path monitoring units 212 of the optical receiving cards 21 W- 1 , . . . , 21 W-n, 21 S- 1 , . . . , 21 S-n to control the selectors 22 - 1 , . . . , 22 -n, so that the selector 22 -i (i=1, . . . , n) selects one of the 1-channel type working optical receiving card 21 W-i and the 1-channel type standby optical receiving card 21 S-i.

In the duplex optical communication system of FIG. 1 , when one working system including one 1-channel type working optical transmitting card 12 W-i and one 1-channel type standby optical receiving card 21 W-i fails, this working system is switched to one standby system including one 1-channel type standby optical transmitting card 12 S-i and one 1-channel type standby optical receiving card 21 S-i, or vice versa, thus realizing a duplex communication.

In the duplex optical communication system of FIG. 1 , however, the optical cards 12 W- 1 ( 21 W- 1 ), . . . , 12 W-n ( 21 W-n), . . . , 12 S- 1 ( 21 S- 1 ), . . . , 12 S-n( 21 S-n) are fixed to one motherboard for the optical transmitting apparatus 1 (the optical receiving apparatus 2 ), as illustrated in FIG. 2 . As a result, when one of the electro-optic converters 122 (the opto-electric converters 211 ) fails, the operation of the entire optical transmitting apparatus 1 (the entire optical receiving apparatus 2 ) has to be stopped, so that the optical card including such a failed converter is replaced with a new one. This deteriorates the efficiency of the maintenance of the duplex communication system.

In FIG. 3 , which illustrates a second prior art duplex optical system, the 1-channel type working optical transmitting cards 12 W- 1 , . . . , 12 W-n of FIG. 1 are combined into an n-channel type working optical transmitting card 12 W, and the 1-channel type standby optical transmitting cards 12 S- 1 , . . . , 12 S-n of FIG. 1 are combined into an n-channel type standby optical transmitting card 12 S.

On the other hand, the 1-channel type working optical receiving cards 21 W- 1 , . . . , 21 W-n of FIG. 1 are combined into an n-channel type working optical receiving card 21 W, and the 1-channel type standby optical receiving cards 21 S- 1 , . . . , 21 S-n of FIG. 1 are combined into an n-channel type standby optical receiving card 21 S.

As a result, the number of components of the system of FIG. 3 is decreased to decrease the manufacturing cost. Note that the operation of the system of FIG. 3 is the same as that of the system of FIG. 1 .

Even in the duplex optical communication system of FIG. 3 , however, the optical cards 12 W( 21 W) and 12 S( 21 S) are fixed to one motherboard for the optical transmitting apparatus 1 (the optical receiving apparatus 2 ), as illustrated in FIG. 4 . As a result, when one of the electro-optic converters 122 (the opto-electric converters 211 ) fails, the operation of the entire optical transmitting apparatus 1 (the entire optical receiving apparatus 2 ) has to be stopped, so that the optical card including such a failed converter can be replaced with a new one. This also deteriorates the efficiency of the maintenance of the duplex communication system.

In FIG. 5 , which illustrates a first embodiment of the present invention, the n-channel type working optical transmitting card 12 W of FIG. 3 is replaced by an n-channel type working optical transmitting card 12 W′ which includes only the monitoring information adding units 121 , and the n-channel type standby optical transmitting card 12 S of FIG. 3 is replaced by an n-channel type standby optical transmitting card 12 S′ which includes only the monitoring information adding units 121 . Each of the electro-optic converters 122 is of a stick type as illustrated in FIG. 6 , and accordingly, each of the electro-optic converters 122 is replaceable. In more detail, each of the electro-optic converters 122 is inserted into a slot (not shown) on the optical transmitting apparatus 1 .

On the other hand, the n-channel type working optical receiving card 21 W of FIG. 3 is replaced by an n-channel type working optical transmitting card 21 W′ which includes only the transmission line monitoring units 212 , and the n-channel type standby receiving optical card 21 S of FIG. 3 is replaced by an n-channel type standby optical receiving card 21 S′ which includes only the transmission line monitoring units 212 . Each of the opto-electric converters 211 is of a stick type as illustrated in FIG. 6 , and accordingly, each of the opto-electric converters 211 is replaceable. In more detail, each of the opto-electric converters 211 is inserted into a slot (not shown) on the optical receiving apparatus 2 .

In the duplex optical communication system of FIGS. 5 and 6 , since the electro-optic converters 122 and the opto-electric converters 211 are of a stick type and accordingly, are replaceable, when one of the electro-optic converters 122 (the opto-electric converter 211 ) fails, such a failed converter is easily replaced with a new one without stopping the operation of the entire optical transmitting apparatus 1 (the entire optical receiving apparatus 2 ). This improves the efficiency of the maintenance of the duplex communication system.

In FIG. 7 , which illustrates a second embodiment of the present invention, one electro-optic converter 122 ′ including a 4-to-1 parallel-to-serial converter is provided instead of the four electro-optic converters 122 for each of the n-channel type working optical transmitting card 12 W and the n-channel type standby optical transmitting card 12 S, and one opto-electric converter 211 ′ including a 1-to-4 serial-to-parallel converter is provided instead of the four opto-electric converters 211 for each of the n-channel type working optical receiving card 21 W and the n-channel type standby optical receiving card 21 S.

The electro-optic converter 122 ′ and the opto-electric converter 211 ′ are also of a stick type as illustrated in FIG. 8 , and accordingly, the electro-optic converter 122 ′ and the opto-electric converter 211 ′ are replaceable. In more detail, the electro-optic converter 122 ′ is inserted into a slot (not shown) on the optical transmitting apparatus 1 , and the opto-electric converter 211 ′ is inserted into a slot (not shown) on the optical receiving apparatus 2 .

Note that the size of the electro-optic converter 122 ′ is four times that of the electro-optic converter 122 , and the size of the opto-electric converter 211 ′ is four times that of the opto-electric converter 211 . Therefore, the motherboard of the optical transmitting apparatus 1 of FIGS. 7 and 8 is the same as that of the optical transmitting apparatus 1 of FIGS. 5 and 6 , and the motherboard of the optical receiving apparatus 2 of FIGS. 7 and 8 is the same as that of the optical receiving apparatus 2 of FIGS. 5 and 6 .

In the duplex optical communication system of FIGS. 7 and 8 , since the electro-optic converter 122 ′ and the opto-electric converter 211 ′ are of a stick type and accordingly, are replaceable, when one of the electro-optic converter 122 ′ (the opto-electric converter 211 ′) fails, such a failed converter is easily replaced with a new one without stopping the operation of the entire optical transmitting apparatus 1 (the entire optical receiving apparatus 2 ). This improves the efficiency of the maintenance of the duplex communication system.

In the duplex optical communication system of FIGS. 7 and 8 , the electro-optic or opto-electric converters use a synchronous digital hierarchy (SDH)/synchronous optical network (SONET). In more detail, each of the converters 122 and 211 is constructed by an optical carrier-level (OC)- 3 /synchronous transport module (STM)- 1 , and each of the converter 122 ′ and 211 ′ is constructed by OC- 12 /STM- 4 . However, the electro-optic converter 122 ′ can be an electro-optic converter including an N-to-1 parallel-to-serial converter (N=2, 3, 4, . . . ), and the opto-electric converter 211 ′ can be an opto-electric converter including a 1-to-N parallel-to-serial converter (N=2, 3, 4, . . . ).

As explained hereinabove, according to the present invention, since a failed electro-optic or opto-electric converter can be replaced with a new one without stopping the operation of the entire system, the efficiency of the maintenance can be improved.