DOI: 10.25549/usctheses-c40-339479
title: Reconfigurable high speed optical signal processing using optical frequency comb for high-capacity, spectrally efficient fiber optic systems and networks

description: Optical fiber communication systems provide the infrastructure for high-capacity data transfer. The field has shown dramatic increases in transmission capacity, and yet the demand for capacity also grows significantly. We are in a situation in which systems must continually grow in capacity to keep pace with the demand, thereby necessitating continual innovation and technical advances. Over the past few years, system capacity increases have been fueled by a combination of coherent technologies and advanced modulation formats. Specifically, coherent transceivers enable systems that can accommodate spectrally efficient modulation formats, in which many bits of information can be transmitted in one bit time to increase the bits/sec/Hz. ❧ To date, efforts to demonstrate flexible and reconfigurable high-capacity communication and signal processing technologies to transmit and process large and high speed data have generally led to a trade-off where reconfigurability of the system is traded for fast transmission speeds and higher capacities. [1-3] This is mainly due to limitations in the bandwidth and linearity of electronic devices. All-optical signal generation and processing not only enables larger bandwidth, but also allows for the encoding of data on amplitude, phase, polarization and frequency of optical wave. All-optical signal processing as a key tool for future flexible and ultrahigh bit-rate optical communication systems could potentially: (i) keep the data in the optical domain to avoid costly optical-to-electrical-to-optical conversion, (ii) be relatively transparent to the specific baud rate and modulation format, and (iii) be capable of handling extremely high data rates. Note that employing optical nonlinearities in a module can potentially meet all these criteria. As a result, intensive research and development is being undertaken on nonlinear optics based devices to achieve the signal processing tasks [4,5]. Nonlinear optics can be used in a variety of applications such as wavelength conversion [6], add-drop multiplexing [7], and quantization [8]. Moreover, the previous works in optical signal processing usually use non-coherent optical waves along with optical delays to perform the signal processing functions that require more nonlinear optical stages which limits the systems performance. In this thesis, we investigate the new approaches of optical signal processing using optical frequency combs to overcome the bottlenecks of the reconfigurable and high capacity optical networks. Using optical frequency combs provide the opportunity of using coherency of the frequency comb lines in order to implement more signal processing functions in the optical domain since many functions require addition of different waves in a coherent fashion. Furthermore, number of optical nonlinear stages could potentially be reduced by utilizing optical frequency. Implementation of different functions such as correlator, Nyquist channel generation, optical data de-aggregation, and coherent homodyne detection of advanced modulation formats are in the scope of this proposal. In fact, these functions could be considered as reconfigurable optical coherent transceiver functionalities which could potentially enable the reconfigurable and agile optical networks.