Performance optimization of hybrid optical amplifiers for dense wavelength division multiplexed system

Abstract

The optical fiber is the enabling and promising technology used in almost all the trunk lines of existing networks. It is also capable of allowing the transmission of many signals over long distances because of its huge transmission bandwidth (in THz) and low losses. For multichannel transmission and to efficiently utilize the fiber bandwidth the dense wavelength division multiplexing (DWDM) is a promising technique, in which a single fiber can independently carry several optical channels with different wavelengths. In optical fiber communication, the attenuation is the major limiting factor imposed by optical components or by fiber itself which degrades the system performance and limits the reach of the signals. To compensate these effects opto-electronic regenerators are used to reshape, retime or retransmit the signal, but simultaneously it increase the cost of the system. On the other hand, optical amplifiers boosts the signals without going through the costly conversions from optical to electrical signal and vice versa. But due to the various non-linear effects and phase noise present in the optical amplifier, its use is restricted to limited applications in optical communications. So, there is demand of optical amplifiers which provide better performance (in term of transient performance, power crosstalk, gain flatness, larger gain bandwidth etc.) for DWDM systems. In order to achieve these objectives it is utmost important to design, characterize and investigate an appropriate optical amplifier for high capacity DWDM systems. As such, new ways to extend the bandwidth, improve the noise and dynamic properties of present-day amplifiers are constantly pursued. This thesis facilitates this process by tracking several system level challenges while acknowledging the limitations of existing devices. The hybrid optical amplifier is an enabling and promising technique for future DWDM multi-terabit systems to minimize the impairments due to fiber nonlinearities and to enhance the gain bandwidth and/or gain flatness.