Monolithically integrated sagnac interferometer for all-optical wavelength conversion

All-optical wavelength conversion in the C-band is demonstrated using a regrowth free monolithically integrated Sagnac interferometer. A single semiconductor optical amplifier (SOA) placed asymmetrically in the loop acts as the non-linear element in the interferometer. Most integrated wavelength converters use the Mach-Zehnder geometry, which requires two SOAs, hence balancing the interferometer becomes an arduous task. The Sagnac geometry, on the other hand, uses a single SOA and the clockwise and the counter clockwise signals traverse the same optical path, thereby negating the effects of optical path length differences. The device is fabricated in the InGaAsP/InP material system grown by gas source molecular beam epitaxy. A tunable (1530-1560 nm) mode locked fiber laser operating at 10 Gb/s was used as the control signal and a distributed feedback (DFB) laser operating at 1540 nm was used as the continuous wave signal. Wavelength conversion observed at 1540 nm with data at 1553 nm is shown Dependence of the on/off extinction ratio on wavelength is shown clearly indicating the uniform performance over the entire C-band. Both up conversion and down conversion is demonstrated by the device.