טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentTselniker Igor
SubjectAdaptive Signal Processing for Ultrahigh-Speed
Photonic Communication:
Carrier Phase, Frequency and
Polarization Recovery
DepartmentDepartment of Electrical Engineering
Supervisor Professor Moshe Nazarathy
Full Thesis textFull thesis text - English Version


Abstract

The ever-growing demand for capacity of optical fiber communication links leads to more complicated and more sophisticated communication schemes. These schemes comprise advanced modulation formats and smart data pre-coding (either single-carrier or OFDM-based ones), ultra-high-speed Analog-to-Digital Converter (ADC) at the receiver and Digital-to-Analog (DAC) at the transmitter, followed by high-speed digital signal processing in the electronic domain. Instead of using only one degree of freedom used in on-off keying, wise deployment of additional parameters naturally inherited in any electrical field is essential. In addition to simultaneous deployment of both amplitude and phase of the transmitted field, signaling with different data over both polarizations and/or multiple transversal modes of the fiber further increase both spectral and power efficiencies.

However, extended use of these degrees of freedom introduces more and more impairments that accompany any optical transmission link. Some of these impairments include:

         Additive White Gaussian Noise (AWGN) originating in optical amplifiers

         Carrier Phase Drifts (CPD) and Carrier Frequency Offsets (CFO) (both present in coherent detection schemes)

         Polarization Multiplexing (PM) and Fiber Mode Division Multiplexing (FMDM) (occurs upon signaling on both polarizations and/or multiple fiber modes)

         Chromatic Dispersion (CD) and Chromatic Mode Dispersion (CMD) (present within broadband transmissions)

         Fiber and Amplifiers Loss (FL)

         Medium non-linearities (present when attempting to increase OSNR by increasing power of transmitted signals)

         In-phase and Quadrature (IQ) imbalance that occurs at detectors

         Quantization noise introduced by the Analogue-to-Digital Converters (DACs)

and so on and so forth. Thus, in order to mitigate the mentioned impairments advanced digital signal processing (DSP) algorithms (both at the transmitter and at the receiver) are highly appealing.

This thesis proposes and investigates different pre-coding schemes for broadband optical communication transmitters (Tx), accompanied with algorithms for broadband optical communication receivers (Rx) introduced in order to mitigate the heretofore mentioned impairments, while providing improved overall performance (in terms of Bit Error Rate (BER), and/or Spectral Efficiency (SE) and/or Power Efficiency). The emphasis will be on maximizing the potential of a variety of adaptive versions of the signal processing algorithms, adaptively learning the system parameters, in effect of performing channel estimation procedures by means of adaptive DSP techniques. The challenges are in the combination of adaptive linear, time-varying and nonlinear digital signal processing - fiber-optic channel estimation and overall receiver adaptation in the context of the ultra-high speed fiber optic transmission.