Modeling of Modulation Formats for Interferometric Noise Mitigation

Interferometric noise in optical communication systems employing reflective modulation schemes can be mitigated by reshaping the data spectrum to reduce the spectral overlap with backscattered and backreflected light. A novel analytical model, capable of analyzing accurately the performance of modulation formats with a wide optical spectrum, is derived here and applied to study the case of interferometric noise caused by Rayleigh backscattering. Compared to more complex models and simulations the new method is fast, simple to implement, and gives clear insight into the physical phenomena involved. In addition, the performance of practical systems can be easily analyzed and optimized due to the capability of the model to include real component specifications such as arbitrary optical and electrical filter responses. The specific case of phase-modulated non-return to zero (PM-NRZ) modulation format is used to validate the model against experimental results and excellent agreement is obtained. The PM-NRZ performance is also investigated as a function of various parameters, quantifying, for example, the trade-off between phase modulation index and interferometric noise mitigation.