Numerical simulation of an integrated laser modulator

In an Integrated Laser Modulator (ILM), residual optical feedback can lead to a significant level of frequency chirp compared to the case of a discrete external modulator. We have developed an original model of the ILM which has been successfully used in the design and optimisation of the ILM. It allows the calculation of static and dynamic properties of the ILM, aiming at a higher output power while keeping the amount of optical frequency chirp as low as possible. This has been obtained on a new ILM generation for which the output power has been multiplied by two by reducing the DFB coupling coefficient. System experiments at 10 Gb/s have demonstrated transmission distance over 76 km without any optical amplifier. The model shows that the chirp depends on the phase of the modulator and laser facets, in agreement with experimental results. Despite the random character of the phase, a low modulator facet reflectivity (/spl les/2/spl times/10/sup -4/) guarantees low feedback induced frequency chirp. Numerical simulation of the response (power and frequency chirp) to a 16-bit pseudo random bit NRZ sequence at 10 Gb/s has been performed.