Analog optical fiber links using Mach-Zehnder modulator (MZM) have numerous applications in cable television (CATV), antenna remoting, optically controlled radar, etc. Currently, performances of these links are hampered by MZM's inherent sinusoidal transfer function. Such nonlinearity not only results in reduced dynamic range, but also limits the number of electrically multiplexed channels for certain application (e.g. CATV). Much effort has been devoted to linearized analog optical fiber link by suppressing the cubic term in MZM's transfer function. These techniques include polarization mixing, dual MZM, and cascaded MZM....[ Read more ]

Analog optical fiber links using Mach-Zehnder modulator (MZM) have numerous applications in cable television (CATV), antenna remoting, optically controlled radar, etc. Currently, performances of these links are hampered by MZM's inherent sinusoidal transfer function. Such nonlinearity not only results in reduced dynamic range, but also limits the number of electrically multiplexed channels for certain application (e.g. CATV). Much effort has been devoted to linearized analog optical fiber link by suppressing the cubic term in MZM's transfer function. These techniques include polarization mixing, dual MZM, and cascaded MZM.

In this thesis, we propose a novel linearization technique for analog fiber links by exploiting the parallelism of wavelength. Compared to conventional schemes mentioned, our scheme maintains the power of fundamental (signal) terms after linearization and thus guarantees a fair comparison of dynamic range. Because of the parallelism in wavelength domain, our proposal offers a more scalable solution and can be generalized for linearization up to (2m-1)-th order by multiplexing m wavelengths.

We experimentally demonstrate our linearization scheme in both amplitude modulation (AM) and phase modulation (PM) systems. By matching the optical power ratio with the ratio of modulation indices of the two wavelengths, third order distortion can be eliminated and dynamic range improvement of 18 and 11 dB have been achieved in AM and PM systems, respectively. The proposed scheme also exhibits excellent robustness to power fluctuations or mismatches among the wavelengths. For power deviation up to 2dB, which is typical for uncooled telecom laser, our proposed system yields a 5dB dynamic range enhancement over unlinearized systems. Effect of chromatic dispersion was also considered, including the dispersion of dual links and of sideband of modulated signal.