GB2121637A - Optical bypass switch - Google Patents

Abstract

An optical bypass in an optical transmission line bridges alternate stations 11a-11d. The stations are each serially connected in the line. A malfunction in a station or in part of the optical line causes the optical bypass to be substituted for the defective station or line section. <IMAGE>

Description

SPECIFICATION Optical bypass switch FIELD OF THE INVENTION This invention relates to data transmission loops which transmit an optical signal from station to station and which employ converters for converting the optical signal to an electrical signal for further processing at each station.

BACKGROUND OF THE INVENTION Bypass switches for maintaining continuity within a loop, especially when a failure occurs at one portion of the loop are well known in the art. Commonly, the occurrence of a failure at one portion of the loop will switch in a bypass around that failed part allowing data to continue to flow and permitting the other stations located in the loop to communicate with each other, notwithstanding the failure.

However, new transmission mediums have been introduced which must be adapted to known loop techniques. One such new transmission media is optical such as an optical fiber through which the data is transmitted in optical form. To further process the data, a converter is connected between the transmission line and each station to convert the optical data to electrical data for processing.

Switching techniques for electrical signals have been well developed. However switching an optical signal from on line to a separate line is not as easily accomplished as electrical switching.

The prior art has not shown a switching capability within an optical transmission line wherein electrical signals are exclusively switched and no optical switching is required, while permitting the continuation of data through a transmission ring in the presence of a discontinuity.

SUMMARY OF THE INVENTION A transmission ring utilizes an optical transmission medium for transmitting data in optical form about the ring. Within the ring are stations serially connected which receive electrical signals and either modify or retransmit those electrical signals to subsequent stations. At the input of each station is a converter for converting the optical signals. At the output of each station is another converter which converts the electrical signals to optical signals for transmission in the optical transmission medium.

Bypassing each station is an optical bypass.

The optical bypass directlty couples the optical transmission line from a preceding station, around a station to a succeeding station. A switching means is provided at the input of each station. The converters are connected to the switching means and the switching means are responsive to the electrical signals converted from the optical signals.

In the disclosed invention, the optical transmission line from the preceding station is connected to a converter which converts the optical signal to an electrical signal. The output of the converter is then connected to a switching means. The optical transmission line connected from the output of the preceding station is also directly coupled to an optical bypass line and, through that optical bypass line, to a converter at the input to a successive station. The switching means at the input of a first station is connected through a converter to an optical bypass line, bypassing the preceding station and connected to the output of a second further preceding station and the input of the converter to the preceding station.

The converted optical data is sensed by the station which produces a valid data or absence of valid data signal through a valid data sensing means. The switching means at the input of the first station for example includes gates which are operated responsive to a valid data signal to either connect the data transmission line from the preceding station to the first station or the optical bypass line through its respective converter from the second further preceding station.In a like manner, a similar switching means at the successive station, responsive to a data signal connects the optical transmission line from the first station through its respective converter to the input of the second station or responsive to the absence of a valid data signal connects the optical bypass line directly coupled to the output of the preceding station, bypassing the first station connecting it to the input of the successive station.

In this invention, the optical bypass line bypassing a first station will be used only when the first station or the direct transmission line between the first and successive station is inoperative. In this way, the optically transmitted signal is preserved through the bypass line.

The system switches electrical signals exclusively. Optical switching is not required, eliminating the additional cost of optical switching elements and loss of signal strength.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a data ring having a bypass for each of the stations in the ring.

Figure 2 shows in greater detail the switch means for decoupling a station from the data ring section and coupling it to a bypass around a preceding station in the ring.

DESCRIPTION OF THE PREFERRED EMBODI MENT A data ring or loop according to the preferred embodiment of the invention may be as shown in Fig. 1. The data ring transmits signals optically from station to station within the ring. The ring comprises ring sections 9am, 9m-b, 9b-c, 9c-d and 9d-a. Each of the optical ring sections designated by numeral 9 interconnects respective stations m and 11 a through 11 d. For example, optical ring section 9d-a connects station 11 d with station 11 a and 9a-m connects station 11 a to the monitor m, etc.

Connected to each of the respective stations 11 a through 11 b is a peripheral device 1 spa through 1 sod respectively.

For the purpose of explanation, data is assumed to be transmitted around the ring in a counterclockwise direction. Each station has a respective preceding station connected by a respective ring section. Within the ring is a monitor m which performs required data house-keeping functions such as checks for data and synchronization errors, etc. Although a monitor is shown in the preferred embodiment it should be understood that the monitor is not essential to the operation of the invention, and this invention applies to other such transmission systems which have no monitor.

A bypass is shown around the monitor, however the monitor bypass will likely be unnecessary as malfunctioning of the monitor and loss of its essential functions will usually prevent operation of the ring.

At the input side of each of the stations 1 a through 11 d is a means for switching the input of each station from a respective ring section to a respective bypass and visa versa.

For example, means 1 2c alternatively connects section 9b-c to succeeding station 11 c, or connects bypass 1 4m-c to station 11 c.

When the bypass 1 4m-c is connected to a succeeding station 11 c, from preceding station m, then station 11 b is effectively bypassed as is the ring section 9b-c between station 1 b and the switching means 12c.

Similar functions are performed by each of the other switching means 1 2d, 1 2a, 1 2m and 1 2d. It being understood that where the monitor performs essential services to the ring, the monitor cannot be effectively bypassed and the bypass means 1 2b and bypass 1 4a-b would be unnecessary. However the bypass means 1 2m to bypass station 11 a through bypass 1 4d-m would be necessary to bypass a defective operating station 11 a or a defective operating ring section 9a-m.

As shown in Fig. 1, each of the switching means can be operated to connect its associated station to either the respective bypass or respective ring section. Additionally, connected to the switching means input, each switching means includes means for converting the optical signal received along any one of the bypasses 1 4 or any of the ring sections 9 to an electrical signal and only electrical signals are switched. Each of the switch means is connected to the input of a respective preceding station by its respective bypass.

In this way, the need for switching optical signals is eliminated and switching may take place more efficiently and more conveniently with the more easily handled electrical signals.

Referring now to Fig. 2, a more detailed view of the switching means, and its interconnection with its respective bypasses and ring sections is shown. As shown in Fig. 2, a portion of the ring including two stations 1 d and 1 a are shown. Each of the stations has a terminal for receiving electrical data, (DIN), and a terminal for transmitting electrical data, (MDOUT).

As shown in Fig. 1, the transmission line 9c-d is connected between station 11 c and switch 1 2d. The optical bypass 1 4b-d is connected to switch 1 2d at its output and as shown in Fig. f, directly to the transmission line 9b-c at the input to switch 1 2c. An optical connection shown as 40 is made between the optical bypass 1 4c-a and the data transmission section 9c-d and similar connections between all other optical bypass lines such as 1 4d-m and its respectively connected transmission line 9d-a.

The optical signal appearing on transmission line section 9c-d also appears on optical bypass line 1 4c-a. Assuming that the data from transmission line section 9c-d is being properly received and converted by optical to electrical converter 43, the electrical signal MDIN will appear at one input of gate 47.

The output of gate 47 will be produced at the input terminal of station 1 d, through or gate 53. When data is being received, then a valid data recognition means, (not shown) recognizing valid data will provide a disabling signal to gate 45. The data received by 1 1d may be retransmitted, modified or new data may be added by station 11 d, which would then appear as MDOUT. MDOUT would be appropriately converted from an optical signal to an electrical signal by converter 55 and transmitted through optical line 9d-a to switch means 1 2a to station 11 a and to the optical bypass line 1 4d-m. The switch 1 2a is shown with parts similarily numbered to that of 1 2d to indicate the same parts operating in the same manner.

When the valid data recognition means of station 1 d senses the absence of valid data, it causes the valid data sensing means to remove the enabling signal from gate 47 through inverter 46 and causes the gate 45 to be enabled. The optical bypass transmission line is mutually exclusive with respect to the operation of its associated data ring section.

Where invalid data is being received from 9cd, the data line section 9c-d is decoupled by switch means 1 2d, the optical bypass line 1 4b-d couples the signal at the output of optical data ring section 9b-c to switch 1 2d, bypassing switch 1 2c, station 11 c, and the line section 9c-d.

The occurrence of an invalid data signal at station 11 d then presumes that a data transmission or processing malfunction exists between the input of station 11 d and the connection of data ring section 9b-c to switch 1 2c. The optical bypass switching arrangement then decouples that stated portion of the optical ring: 12c, station 11 c, and line 9c-d.

Invalid data sensing means in any of the other stations 11 a, 11 b, 11 c would cause a similar decoupling of the respective ring sections and coupling of the respective optical bypass. The data signal as stated above in line 9c-d also appears through optical connection 40 on optical bypass line 1 4c-a. An enabling signal produced by inverter 46 responsive to the invalid data sensing signal of station 11 a then enables gate 45 coupling line optical bypass line 1 4c-a to the succeeding station 11 a from preceding station 11 c and bypassing switch 1 2d, station 11 d, and data ring section 9d-a.

The connection 40 of the optical bypass to the data ring section may be made through such known devices as a T-coupler or a starcoupler and may be any device by which the optical bypass line is permanently affixed to the data transmission line, avoiding switching of optical lines. As shown, all switching is done after the conversion of the optical signal into an electrical signal. The electrical signal is switched so that for each respective pair of optical bypass lines and a data ring section the switching means causes the coupling and decoupling of the two said lines in a mutually exclusive fashion.

The respective pair of optical transmission bypass lines and data transmission lines shown are 1 4c-a and 9d-a, 1 4d-m and 9a-m, 14a-b and 9m-b, 14m-c and 9b-c, and 14b-d and line 9c-d.

By use of the optical bypass, optical switching is avoided.

Claims (12)

1. An optical data transmission line comprising stations serially connected in the line and optical bypasses for coupling the transmission line from a preceding station, around an intermediate station to a succeeding station, having an input means connected to the optical transmission line for receiving optical signals from an intermediate station and including a means for converting said optical signals into electrical signals and for producing a valid data signal, responsive to valid optical data being received, said input means including switching means, said switching means having an input connected to said means for converting and being responsive to said valid data signal, an optical bypass means, having its output connected to said input means and its input connected to the output of a preceding station, said switching means, connecting said optical transmission line from said intermediate station, into said succeeding station in response to said valid data signal, or disconnecting said optical transmission line from said succeeding station, in response to the absence of the said valid data signal, and connecting said optical bypass line from the output of said preceding station to said succeeding station and bypassing said intermediate station.

2. An optical transmission line according to claim 1 including a plurality of stations, each station of said plurality of stations having said input means and being connected by a respective optical bypass to respective preceding stations.

3. An optical transmission line system according to claim 2 wherein the optical transmission line is a ring.

4. An optical transmission line system according to claim 1 wherein said switching means includes gate means, said gate means including a first gate connected to said transmission line and a second gate connected to said optical bypass line and said gate means being responsive to the presence of a valid data signal for enabling said first gate and disabling said second gate.

5. An optical transmission line system according to claim 4 where said means for producing the said valid data signal provides an enabling signal for said second gate in the absence of said valid data signal, and provides a disabling signal to said first gate.

6. An optical bypass for an optical data transmission ring including, a) stations connected in said transmission ring, each of said stations having its input connected to the output of a preceding station in the ring and its output connected to the input of a succeeding station in the ring.

b) at least a first optical bypass for a first station in said ring having its input connected to the output of a preceding station and its output connected to a succeeding station, relative to said first station, switching means connected to said succeeding station, said switching means being responsive to valid data appearing on the said ring from said first station for coupling said ring to said succeeding station and being responsive to invalid data appearing on said ring from said first station for decoupling said transmission ring and coupling said bypass from said preceding station to said succeeding station.

7. An optical bypass according the claim 6 wherein said switching means includes a convertor for converting the optical signal, appearing on the bypass or on the said ring, to an electrical signal, said switching means including means responsive to said electrical signal for indicating valid data or invalid data on the said ring and said switching means being responsive to the absence of said valid data indication for decoupling said ring and coupling said bypass to said succeeding station.

8. A method of bypassing optical data in a data transmission ring including the steps of connecting a series of stations in an optical data ring for transmitting optical data to ring stations and for receiving optical data from ring stations, comprising a) connecting bypasses for transmitting optical data from a preceding station fo a successive station and past an intermediate station between said preceding and successive stations, b) generating a valid data signal at each of said stations in response to valid data being received over said ring, and c) responsive to the absence of said valid data signal at a successive station, uncoupling said data ring connecting said successive station from said intermediate station and coupling said successive station to a preceding station through said optical bypass.

9. A method of bypassing optical data according to claim 8 wherein said step of generating a valid data signal includes the step of converting said optical data into electrical valid and invalid data signals.

10. A method of bypassing optical data according to claim 7 wherein said step of uncoupling and coupling is responsive to said electrical valid and invalid data signals.

11. An optical data transmission line capable of operating substantially as hereinbefore described with reference to Figs. 1 and 2 of the accompanying drawings.

12. A method of bypassing optical data in a data transmission ring substantially as hereinbefore described with reference to Figs. 1 and 2 of the accompanying drawings.