TASA: a TDM ASA-based optical packet switch

• US 20180167702A1
• Filed: 12/14/2016
• Published: 06/14/2018
• Est. Priority Date: 12/14/2016
• Status: Active Grant

• Current Assignee: Chin-Tau Lea
• Original Assignee: Chin-Tau Lea
• Inventors: Lea, Chin-Tau
• Granted Patent: US 10,499,125 B2
• Time in Patent Office: Days
• CPC Class Codes: H04J 14/02 Wavelength-division multiplex systems
• CPC Class Codes: H04Q 11/00 Selecting arrangements for multiplex systems multiplex systems H04J
• CPC Class Codes: H04Q 11/0005 Switch and router aspects
• CPC Class Codes: H04Q 2011/0022 using fibre gratings

Abstract

A scalable AWGR-based optical packet switch, called TASA (short for TDM ASA), is presented in this invention. The switch is a modified version of the ASA switch but does not have its drawbacks. The total port count is N² and each port can transmit up to N packets of different wavelengths simultaneously. This makes the total capacity of the switch close to (N³×bandwidth of one wavelength channel).

But a TASA switch differs from an ASA switch in two major ways. First, a TASA switch does not need an electronic scheduler. This removes a potential bottleneck in the design of an optical packet switch. Second, it can handle any kind of unbalanced loads and can tolerate faults. These qualities, however, are missing in an ASA switch.

Claims

1. An optical switch fabric comprising:

a first switching stage comprising a plurality of N×

N (N input ports and N output ports) AWGRs (arrayed wavelength grating routers) for cyclically routing component wavelengths, each component wavelength carrying a data packet, of first WDM signals received from external processors and sending first routed WDM signals to a second switching stage;

the second switching stage comprising a plurality of N×

N optical space switches, operating in a pre-determined TDM (time division multiplexing) mode, to switch the first routed WDM signals to a third switching stage; and

the third switching stage comprising a plurality of N×

N AWGRs for cyclically routing component wavelengths of second WDM signals, received from the second stage, to output ports of the plurality of AWGRs of the third stage.

2. The switch fabric of claim 1, wherein N is an odd integer.

3. The switch fabric of claim 2, wherein the second space switching stage comprises N optical space switches numbered from 0 to N 1.

4. The switch fabric of claim 3, wherein the first and the third switching stage comprise m AWGRs numbered from 0 to m−

1, and m≤

N.

5. The system fabric of claim 4, wherein address of each input port of the first switching stage is represented by a two tuple (group, member), 0≤

group ≤

m−

1, 0≤

member≤

N−

1, group being an AWGR number in the first switching stage and member being an input port number of said AWGR.

6. The switch fabric of claim 5, wherein address of each output port of the third switching stage is represented by a two tuple (group, member), 0≤

group≤

(m−

1), and 0≤

member≤

N−

1, group being an AWGR number in the third switching stage and member being an output port of said AWGR.

7. The switch fabric of claim 6, wherein external processor connected to input port (g₁,m₁), g₁ being a group value and mi a member value, of the first switching stage uses wavelength w to transmit data packets destined for external processor connected to output port (g2,m2), g2 being a group value and m2 a member value, of the third switching stage, wherein w is computed from

m₂=(m₁+2w) mod N.

8. A switching system comprising:

a first optical switch fabric, a middle-stage comprising a plurality of port processors, and a second optical switch fabric, wherein the first and the second optical switch fabric comprise a first switching stage comprising m N×

N AWGRs, numbered from 0 to m−

1, for cyclically routing component wavelengths, each component wavelength carrying a data packet, of first WDM signals received from external processors and sending first routed WDM signals to a second switching stage;

the second switching stage comprising N N×

N optical space switches, numbered from 0 to N−

1, operating in a pre-determined TDM (time division multiplexing) mode to switch the first routed WDM signals to a third switching stage; and

the third switching stage comprising m N×

N AWGRs, numbered from 0 to m−

1, for cyclically routing component wavelengths of second WDM signals, received from the second stage, to output ports of the plurality of AWGRs of the third stage.

9. The switching system of claim 8, wherein N is an odd integer and m≤

N.

10. The switching system of claim 9, wherein address of each input port of the first and the second optical switch fabric is represented by a two tuple (group, member), 0≤

group≤

m−

1 , 0≤

member≤

N−

1, group being an AWGR number in the first switching stage of the fabric and member being an input port number of said AWGR.

11. The switching system of claim 10, wherein address of each output port of the first and the second optical switch fabric is represented by a two tuple (group, member), 0≤

group≤

(m−

1), and 0≤

member≤

N−

1, group being an AWGR number in the third switching stage of the fabric and member being an output port of said AWGR.

12. The switching system of claim 11, wherein an external port processor randomly selects a middle-stage port processor as the destination of an incoming packet and sends the packet to the selected middle-stage port processor through the first optical switch fabric, and the selected port processor sends the packet to its original destination output port through the second optical switch fabric.

13. The switch system of claim 12, wherein external processor connected to input port (g₁,m₁), g₁ being a group value and ml a member value, of the first optical switch fabric uses wavelength w to transmit data packets destined for a middle-stage port processor connected to output port (g₂,m2), g₂ being a group value and m₂ a member value, of the first optical switch fabric, wherein w is computed from

m₂=(m₁+2w) mod N.