# Frequency-Modulated Microwave Photonic Links with Direct Detection: Review and Theory

### John Wyrwas

###
EECS Department

University of California, Berkeley

Technical Report No. UCB/EECS-2010-156

December 15, 2010

### http://www.eecs.berkeley.edu/Pubs/TechRpts/2010/EECS-2010-156.pdf

This work is a theoretical study of microwave photonic links which use optical frequency modulation (FM) and filter-slope discrimination for demodulation. The high modulation efficiency of optical FM devices is attractive for achieving low noise-figure links, but linear demodulation of the signals is also desired. In order to design discriminators which produce low distortion, this paper presents general full-signal and small-signal models of the effects of arbitrary optical filtering on an FM link, including the interaction between FM and residual IM. The small signal model is used to derive figures of merit for the linearity, noise and dynamic range of the FM links. The results of the models invalidate a common assumption: that linear FM to IM discrimination is possible. Instead, the discrimination must be from FM to amplitude modulation of the electric field for the link response to be linear.

The linearity of links using two different sets of FIR discriminator filters, designed using the minimax relative error and maximally linear criteria, are compared in order to evaluate the better design method. The evolution of link linearity with filter order is studied. The analytical models are compared to numerical simulations of the filters, and the models are found to be consistent. Finally, a Monte Carlo simulation is used to analyze the sensivity to errors in fabrication for high-order filters realized in planar lightwave circuits (PLC) with a lattice filter architecture.

**Advisor:** Ming C. Wu

BibTeX citation:

@mastersthesis{Wyrwas:EECS-2010-156, Author = {Wyrwas, John}, Editor = {Wu, Ming C.}, Title = {Frequency-Modulated Microwave Photonic Links with Direct Detection: Review and Theory}, School = {EECS Department, University of California, Berkeley}, Year = {2010}, Month = {Dec}, URL = {http://www.eecs.berkeley.edu/Pubs/TechRpts/2010/EECS-2010-156.html}, Number = {UCB/EECS-2010-156}, Abstract = {This work is a theoretical study of microwave photonic links which use optical frequency modulation (FM) and filter-slope discrimination for demodulation. The high modulation efficiency of optical FM devices is attractive for achieving low noise-figure links, but linear demodulation of the signals is also desired. In order to design discriminators which produce low distortion, this paper presents general full-signal and small-signal models of the effects of arbitrary optical filtering on an FM link, including the interaction between FM and residual IM. The small signal model is used to derive figures of merit for the linearity, noise and dynamic range of the FM links. The results of the models invalidate a common assumption: that linear FM to IM discrimination is possible. Instead, the discrimination must be from FM to amplitude modulation of the electric field for the link response to be linear. The linearity of links using two different sets of FIR discriminator filters, designed using the minimax relative error and maximally linear criteria, are compared in order to evaluate the better design method. The evolution of link linearity with filter order is studied. The analytical models are compared to numerical simulations of the filters, and the models are found to be consistent. Finally, a Monte Carlo simulation is used to analyze the sensivity to errors in fabrication for high-order filters realized in planar lightwave circuits (PLC) with a lattice filter architecture.} }

EndNote citation:

%0 Thesis %A Wyrwas, John %E Wu, Ming C. %T Frequency-Modulated Microwave Photonic Links with Direct Detection: Review and Theory %I EECS Department, University of California, Berkeley %D 2010 %8 December 15 %@ UCB/EECS-2010-156 %U http://www.eecs.berkeley.edu/Pubs/TechRpts/2010/EECS-2010-156.html %F Wyrwas:EECS-2010-156