The impact of phase conjugation on the nonlinear-Shannon limit:the difference between optical and electrical phase conjugation

We show that optical and electrical phase conjugation enable effective nonlinear compensation, The impact of polarization mode dispersion and finite processing bandwidth on the ultimate limits are also considered.

Polarization switchable single/multi-wavelength fiber ring laser with an intra-cavity all fiber Lyot filter

we demonstrate a polarization switchable, single/ multi-wavelength fiber ring laser based on an intra-cavity all fiber Lyot filter. The laser can operate at single-, multi-wavelength by adjusting polarization controller, and givessingle polarization output. © 2015 OSA.

Advanced digital signal processing for coherent optical OFDM transmissions

Coherent optical orthogonal frequency division multiplexing (CO-OFDM) has been actively considered as a potential candidate for long-haul transmission and 400 Gb/s to 1 Tb/s Ethernet transport because of its high spectral efficiency, efficient implementation, flexibility and robustness against linear impairments such as chromatic dispersion and polarization mode dispersion. However, due to the long symbol duration and narrow subcarrier spacing, CO-OFDM systems are sensitive to laser phase noise and fibre nonlinearity induced penalties. As a result, the development of CO-OFDM transmission technology crucially relies on efficient techniques to compensate for the laser phase noise and fibre nonlinearity impairments. In this thesis, high performance and low complexity digital signal processing techniques for laser phase noise and fibre nonlinearity compensation in CO-OFDM transmissions are demonstrated. For laser phase noise compensation, three novel techniques, namely quasipilot-aided, decision-directed-free blind and multiplier-free blind are introduced. For fibre nonlinear compensation, two novel techniques which are referred to as phase conjugated pilots and phase conjugated subcarrier coding, are proposed. All these abovementioned digital signal processing techniques offer high performances and flexibilities while requiring relatively low complexities in comparison with other existing phase noise and nonlinear compensation techniques. As a result of the developments of these digital signal processing techniques, CO-OFDM technology is expected to play a significant role in future ultra-high capacity optical network. In addition, this thesis also presents preliminary study on nonlinear Fourier transform based transmission schemes in which OFDM is a highly suitable modulation format. The obtained result paves the way towards a truly flexible nonlinear wave-division multiplexing system that allows the current nonlinear transmission limitations to be exceeded.

Femtosecond laser inscription of fiber bragg gratings with low insertion loss and minor polarization dependence

The inscription of low insertion loss and negligibly polarization dependent fiber Bragg gratings inscribed using a femtosecond laser system is reported. Insertion losses were <0.4dB/20mm and polarization wavelength shift of <5pm, with transmission changes <0.1dB. © 2010 Optical Society of America.

Impact of optical phase conjugation on the nonlinear Shannon limit

Compensation of the detrimental impacts of nonlinearity on long-haul wavelength division multiplexed system performance is discussed, and the difference between transmitter, receiver and in-line compensation analyzed. We demonstrate that ideal compensation of nonlinear noise could result in an increase in the signal-to-noise ratio (measured in dB) of 50%, and that reaches may be more than doubled for higher order modulation formats. The influence of parametric noise amplification is discussed in detail, showing how increased numbers of optical phase conjugators may further increase the received signal-tonoise ratio. Finally the impact of practical real world system imperfections, such as polarization mode dispersion, are outlined.