Optical transmission systems including optical switching devices, control apparatuses, and methods

• US 6,771,905 B1
• Filed: 06/06/2000
• Issued: 08/03/2004
• Est. Priority Date: 06/07/1999
• Status: Expired due to Term

• Current Assignee: Optic153 LLC (Equitable IP Corporation)
• Original Assignee: Corvita Corporation (Boston Scientific Corporation)
• Inventors: Bortz, Michael
• Primary Examiner(s): Pascal, Leslie
• Assistant Examiner(s): SINGH, DALZID E
• Application Number:
  US09/588,526
• Time in Patent Office: 1,519 Days
• Field of Search: 398/48, 398/56, 398/84, 398/85, 398/45, 398/83
• US Class Current: 398/45
• CPC Class Codes: H04J 14/02 Wavelength-division multiplex systems
• CPC Class Codes: H04J 14/0204 Broadcast and select arrangements, e.g. with an optical splitter at the input before adding or dropping
• CPC Class Codes: H04J 14/0205 Select and combine arrangements, e.g. with an optical combiner at the output after adding or dropping
• CPC Class Codes: H04J 14/0212 using optical switches or wavelength selective switches [WSS]
• CPC Class Codes: H04J 14/0217 Multi-degree architectures, e.g. having a connection degree greater than two
• CPC Class Codes: H04J 14/0221 Power control, e.g. to keep the total optical power constant
• CPC Class Codes: H04Q 11/0005 Switch and router aspects
• CPC Class Codes: H04Q 2011/0016 using wavelength multiplexing or demultiplexing
• CPC Class Codes: H04Q 2011/0049 Crosstalk reduction; Noise; Power budget

Abstract

The optical systems of the present invention include optical switching device generally configured to control signal characteristic profiles over the pluralities of signal channels, or wavelengths, to provide desired signal characteristic profiles at the output ports of the device. Various signal characteristics that can be controlled include power level, cross-talk, optical signal to noise ratio, etc. The optical switching devices can include balanced demultiplexer/multiplexer combinations and switches that provide for uniform optical loss through the devices. In addition, low extinction ratio switches can be configured to provide higher extinction ratios.

Claims

1. An optical transmission system comprising:

at least one optical transmitter configured to transmit at least one optical signal channel via an optical signal along an optical path;

at least one optical receiver configured to receive at least one optical signal channel from said optical path; and

,

an optical switching device disposed along said optical path including

a demultiplexer configured to demultiplex the optical signal provided to an input port a plurality of signal groups including at least one signal channel,

a switch element configurable to pass or prevent the passage of at least one of the signal groups and variably control the optical power of the signal groups passing through said switch element, and

a multiplexer configured to multiplex the signal groups passed by said switch element into an output signal through an output port in optical communication with said optical receiver, wherein said optical switching device imparts a substantially uniform optical loss across the at least one optical signal channels;

an optical amplifier disposed along said optical path including an optical amplifying medium having an input and an output and configured to amplify optical signals passing through said amplifying medium when said amplifying medium is supplied with power;

a power source configured to supply power to said amplifying medium, wherein the power supplied by said power source is controlled to maintain a constant output power for each signal channel in the optical signals after passing through said amplifying medium,

an input power monitor configured to monitor optical signal power proximate said input of said amplifier;

an output power monitor configured to monitor optical signal power proximate said output of said amplifier;

a comparator configured to vary the power supplied by said power source based on the optical signal power at said amplifier input and output and a gain set point; and

,

central processor configured to vary the gain set point of the comparator based on the number of signal channels and the optical signal power at said input to said amplifier.

2. The system of claim 1, wherein said demultiplexer and said multiplexer are configured such that each signal group passing through said demultiplexer and said multiplexer encounters a plural total number of band-pass stages and band-stop stages and an equal number of band-pass stages and an equal number of band-stop stages.

3. The system of claim 1, wherein said demultiplexer, said switch element, and said multiplexer are configured such that each signal group passing through said demultiplexer and said multiplexer encounters a plural total number of band-pass stages and bandstop stages and an equal number of band-pass stages and band-stop stages.

4. The system of claim 1, wherein said demultiplexer and said multiplexer include at least one multi-port device selected from the group consisting of optical circulators, couplers, splitters, arrayed waveguides, diffraction gratings, prisms, and combinations thereof, wherein each of the signal groups passing through the demultiplexer and multiplexer passes through the same total number of multi-port devices.

5. The system of claim 1, wherein said demultiplexer and said multiplexer include at least one wavelength selective device selected from the group consisting of fiber and free space, gratings, Fabry-Perot filters, dichroic filters, wavelength selective couplers and splitters, arrayed waveguides, and combinations thereof.

6. The system of claim 1, wherein said switch element includes a plurality of switch elements corresponding to the plurality of signal groups provided by said demultiplexer, each of said switch elements being configurable to pass or substantially prevent the passage of the corresponding signal group to said multiplexer.

7. The system of claim 6, wherein said optical switching device includes:

a plurality of demultiplexers and corresponding switch elements, each demultiplexer configured to receive optical signals via corresponding input ports,

a plurality of multiplexers configured to receive signal groups from said corresponding switch elements and provide a plurality of multiplexed signal groups to corresponding output ports.

8. The system of claim 1, wherein said optical switching device further includes:

an optical amplifier disposed along said optical path including an optical amplifying medium having an input and an output and configured to amplify optical signals passing through said amplifying medium when said amplifying medium is supplied with power;

a power source configured to supply power to said amplifying medium, wherein the power supplied by said power source is controlled to maintain a constant output power for each signal channel in the optical signals after passing through said amplifying medium.

9. The system of claim 8, wherein said optical amplifier is configured to compensate for input signal group power variations and non-uniform loss imparted to the signal groups by at least one of said demultiplexer, said switch element, and said multiplexer.

10. The system of claim 1, wherein said central processor is provided with the number of channels based on at least one of channel identifier signals, optical signal power, and optical spectrum analysis.

11. The system of claim 1, wherein said central processor compares the provided number of channels with an expected number of channels provided by a network management system.

12. The system of claim 1, wherein:

said optical amplifying medium is an erbium doped fiber;

said power source is at least one laser configured to supply optical energy to said erbium doped fiber.

13. The system of claim 1, wherein said at least one laser provides optical power in at least one of the 980 nm and 1480 nm wavelength range and the signal channels are in the 1550 nm wavelength range.

14. The system of claim 1, wherein said amplifier is further configured to serve as said switch element and to perform optical amplification, on/off switching and power equalization of the signal group provided to said switch element.

15. An optical transmission system comprising:

at least one optical transmitter configured to transmit at least one optical signal channel via an optical signal along an optical path;

at least one optical receiver configured to receive at least one optical signal channel from said optical path; and

,

an optical switching device disposed along said optical path including

a demultiplexer configured to demultiplex the optical signal provided to an input port a plurality of signal groups including at least one signal channel,

a switch element configurable to pass or prevent the passage of at least one of the signal groups and variably control the optical power of the signal groups passing through said switch element, wherein said switch element is configured to pass the signal group in a first configuration and attenuate the signal group in a second configuration;

a saturable absorber optically connecting said switch fabric and said multiplexer and configured to pass the signal group to said multiplexer when the switch fabric is in the first configuration and absorb the signal group when the switch fabric is in the second configuration; and

a multiplexer configured to multiplex the signal groups passed by said switch element into an output signal through an output port in optical communication with said optical receiver, wherein said optical switching device imparts a substantially uniform optical loss across the at least one optical signal channels.

16. The system of claim 15, wherein said switch element is selected from the group consisting of thermo-optic switches, acousto-optic switches, mechanical line and micro-mirror switches, liquid crystal switches, doped fiber and semiconductor amplifier switches, tunable filters, and combinations thereof.

17. The system of claim 15, wherein said saturable absorber includes doped fiber and semiconductor amplifiers.

18. The system of claim 17, wherein said saturable absorber includes an unpumped erbium doped fiber.

19. The system of claim 15, wherein said switch element includes:

an input port optically connected to said demultiplexer and to a first input/output port in a first switch configuration and to a second input/output port in a second switch configuration;

an output port optically connected to said multiplexer and to the second input/output port in the first switch configuration and to the first input/output port in the second switch configuration;

a waveguide optically connecting said first input/output port to said second input/output port; and

,

an optical isolator disposed along said waveguide and configured to optically isolate said first input/output port from optical energy passing through said waveguide from said second input/output port.

20. The system of claim 19, wherein said input port and said output port are optically connected to said first and second input/output ports via a crossbar switch configured such that in the first switch configuration said crossbar switch impedes optical communication between said input port and said second input/output port and between said output port and said first input/output port and in the second switch configuration said crossbar switch impedes optical communication between said input port and said first input/output port and between said output port and said second input/output port.

21. The system of claim 20, wherein said crossbar switch includes thermo-optic switches, acousto-optic switches, mechanical line and micro-mirror switches, liquid crystal switches, doped fiber and semiconductor amplifier switches, tunable filters, and combinations thereof.