Low noise colorless, directionless, contentionless reconfigurable optical add/drop multiplexer
Methods and systems for implementing a low noise CDC ROADM include incorporating individual stages of an optical PSA before and after WSSs included in the CDC ROADM. The WSSs may be used to route the pump and idler signals, as well as to perform phase tuning for optimal phase-sensitive amplification.
1. A method for operating reconfigurable optical add/drop multiplexers (ROADM) in optical transport networks, the method comprising:
receiving an input wavelength division multiplexing (WDM) optical signal at an input degree of a ROADM;
transmitting the input WDM optical signal through a phase sensitive amplifier (PSA) stage I, wherein the PSA stage I comprises a first non-linear optical element (NLE) through which the input WDM optical signal and a first pump wavelength are passed to generate a PSA stage I optical signal comprising the input WDM optical signal, the first pump wavelength, and an idler signal;
transmitting the PSA stage I optical signal through a first wavelength selective switch (WSS);
receiving wavelengths for a PSA stage II optical signal at a second WSS, the PSA stage II optical signal comprising wavelengths included in an output WDM optical signal, the first pump wavelength, and corresponding idler signals;
subsequent to the second WSS, transmitting the PSA stage II optical signal to a PSA stage II, wherein the PSA stage II comprises a second NLE through which the PSA stage II optical signal is amplified to generate the output WDM optical signal i and
at the PSA stage II, prior to the second NLE, transmitting the PSA stage I signal through a third NLE through which a second pump wavelength is counterpropagated, wherein the third NLE and the second pump wavelength perform Raman amplification on the PSA stage I signal.
2. The method of claim 1 , further comprising:
passing the PSA stage II optical signal through an optical band pass filter to remove the pump wavelength and the idler signals to isolate the output WDM optical signal;
transmitting the output WDM optical signal through an output degree of the ROADM.
3. The method of claim 2 , wherein the output degree of the ROADM is a drop port.
4. The method of claim 1 , wherein the input degree of the ROADM is an add port.
5. The method of claim 1 , further comprising:
using the first WSS to phase tune the PSA stage I optical signal, wherein respective phases of the input WDM optical signal, the pump wavelength, and the idler signal are aligned.
6. The method of claim 5 , wherein the respective phases are aligned based on a feedback signal from an optical channel monitor monitoring the output WDM optical signal.
7. A reconfigurable optical add/drop multiplexer (ROADM), comprising:
a phase sensitive amplifier (PSA) stage I to receive an input wavelength division multiplexing (WDM) optical signal at an input degree of the ROADM, wherein the PSA stage I comprises a first non-linear optical element (NLE) through which the input WDM optical signal and a first pump wavelength are passed to generate a PSA stage I optical signal comprising the input WDM optical signal, the first pump wavelength, and an idler signal;
a first wavelength selective switch (WSS) cross connect comprising a first WSS enabled to receive the PSA stage I optical signal;
a second wavelength selective switch (WSS) cross connect comprising a second WSS enabled to receive a PSA stage II optical signal, the PSA stage II optical signal comprising wavelengths included in an output WDM optical signal, the first pump wavelength, and corresponding idler signals;
a PSA stage II to receive the PSA stage II optical signal, wherein the PSA stage II comprises a second NLE through which the PSA stage II optical signal is amplified to generate the output WDM optical signal; and
a third NLE at the PSA stage II, prior to the second NLE, receiving the PSA stage I signal and receiving a second pump wavelength in a counterpropagating direction to the PSA stage I signal, wherein the third NLE and the second pump wavelength perform Raman amplification on the PSA stage I signal.
8. The ROADM of claim 7 , further comprising:
an optical band pass filter through which the PSA stage II optical signal is passed through after the PSA stage II to remove the pump wavelength and the idler signals to isolate the output WDM optical signal at an output degree of the ROADM.
9. The ROADM of claim 8 , wherein the output degree of the ROADM is a drop port.
10. The ROADM of claim 7 , wherein the input degree of the ROADM is an add port.
11. The ROADM of claim 7 , wherein the first WSS is used to phase tune the PSA stage I optical signal, wherein respective phases of the input WDM optical signal, the pump wavelength, and the idler signal are aligned.
12. The ROADM of claim 11 , wherein the respective phases are aligned based on a feedback signal from an optical channel monitor monitoring the output WDM optical signal.