All-optical interferometer provides efficient signal regeneration

Researchers from the Technical University of Denmark (Lyngby, Denmark) and from the Alcatel Corporate Research Center (Marcoussis, France) have demonstrated all-optical wavelength conversion at 40 Gbit/s using an SOA-based, all-active Mach-Zehnder interferometer (MZI).

In the experimental setup, a 40-Gbit/s, 1554-nm return-to-zero input signal was generated by passively multiplexing 10-GHz pulses from a gain-switched, distributed-feedback (DFB) laser (see figure). The optical signal-to-noise ratio (OSNR) in the signal was controlled by a sub-block consisting of a variable attenuator, an erbium-doped fiber amplifier (EDFA), and an optical filter. 2R regeneration of the input signal through the MZI produced a 1547-nm continuous-wave output with an OSNR in excess of 37 dB, while the input OSNR varied from just under 14 dB to just over 26 depending on the input power at the EDFA. The all-optical 2R regenerator produced a clear and open eye diagram with an extinction ratio on the order of 10 dB, while introducing a low penalty on the order of 0.6 dB at 40 Gbit/s.

The researchers also demonstrated a capability for all-optical 3R regeneration by providing a 40-GHz clock signal to the MZI that was extracted from the data signal. The clock was simulated by modulating a 1547-nm, gain-switched DFB laser at 10 GHz and passively multiplexing it to 40 GHz prior to feeding it into one of the MZI inputs. The return-to-zero signal format was preserved at the output, with a low penalty on the order of 0.5 dB at 40 Gbit/s. For more details, contact D. Wolfson at [email protected].

All-active Mach-Zehnder interferometer provided all-optical 2R regeneration and demonstrated capability for 3R regeneration at 40 Gbit/s.