Dual correlated pumping scheme for phase noise preservation in all-optical wavelength conversion

Abstract

We study the effect of transfer of phase noise in different four wave mixing schemes using a coherent phase noise measurement technique. The nature of phase noise transfer from the pump to the generated wavelengths is shown to be independent of the type of phase noise (1 / f or white noise frequency components). We then propose a novel scheme using dual correlated pumps to prevent the increase in phase noise in the conjugate wavelengths. The proposed scheme is experimentally verified by the all-optical wavelength conversion of a DQPSK signal at 10.7 GBaud.

Simulations of an OSNR-Limited All-Optical Wavelength Conversion Scheme

“…2. Dual pumps with correlated phase-noise can be created by filtering out appropriate spectral lines from an OCG [6] with the assistance of a wavelength selective switch (WSS). Based on the wavelength of the incoming packet and the wavelength to which the packet is being converted to, the network management controls the WSS to filter the two specific pump lines from the OCG.…”

“…The pumps possess correlated phase-noise  p ; also shown is the complex conjugate of the pumps to aid the visualization of the angles of the idlers. The nondegenerate idler that experiences phase-noise cancellation is * 21 P S P E E E , because phase-noise from the pumps cancels due to the conjugation of one of the pumps [6] and this idler is an exact scaled copy of the original signal as shown in Fig. 4.…”

“…using two pump lasers [4], [5], have relied upon using separate pump lasers with linewidths around 100 kHz, and demonstrate good performance for single-stage wavelength conversion. To circumvent the phase-noise transfer problem, recently it was shown for the conversion of DQPSK signals [6], that if the two pumps are coherent, i.e. both pumps possess the same phase noise, then the DQPSK signal could be converted without incurring any phase-noise transfer from the pumps.…”

“…both pumps possess the same phase noise, then the DQPSK signal could be converted without incurring any phase-noise transfer from the pumps. Pumps with correlated phase noise could be derived from optical comb generators (OCG), which are optical sources containing many spectral lines with equidistant frequency spacing and the lines possessing correlated phase-noise; examples of which would be: mode locked lasers [6]; sinusoidally modulated single-mode lasers such as gainswitched lasers [7] and cascaded optical phase modulators [8]. [6], we are simulating a variation of the nondegenerate FWM scheme that allows for the conversion of the input signal to any wavelength within the SOA gain bandwidth; whereas in [6] the signal was up and down converted by the frequency difference between two pumps created by carrier-suppressed amplitude modulation in a Mach-Zehnder modulator.…”

“…Pumps with correlated phase noise could be derived from optical comb generators (OCG), which are optical sources containing many spectral lines with equidistant frequency spacing and the lines possessing correlated phase-noise; examples of which would be: mode locked lasers [6]; sinusoidally modulated single-mode lasers such as gainswitched lasers [7] and cascaded optical phase modulators [8]. [6], we are simulating a variation of the nondegenerate FWM scheme that allows for the conversion of the input signal to any wavelength within the SOA gain bandwidth; whereas in [6] the signal was up and down converted by the frequency difference between two pumps created by carrier-suppressed amplitude modulation in a Mach-Zehnder modulator. The calculated bit error rate (BER) results show that the converted signal shows almost identical performance to the back-to-back performance of the original signal even when the linewidth of a single comb line is 10 MHz; thus proving that the scheme works regardless of the level of phase noise on the pumps, provided both pump lines have correlated phasenoise.…”