Sean O'Duill

Optical multicarrier based IM/DD DWDM-SSB-OFDM access networks with SOAs for power budget extension

We report on the use of a SOA for simultaneous amplification of multicarrier, 10×12.5 Gb/s, DWDM-SSB-OFDM downstream signals finding negligible penalty at FEC limit compared to EDFAs. The scheme allows for a 128 passive split and transmission over 50 km.

Integrated frequency combs for flexible optical networks

Optical frequency comb (OFC) sources have proven to be useful in applications such as frequency metrology [1], spectroscopy [2], millimetre wave generation [3] and dense/ultra-dense wavelength division multiplexed high speed optical communications [4]. These applications require highly coherent, stable and cost efficient optical comb sources. Other important comb parameters include a flexible free spectral range (FSR) and uniform power distribution amongst the frequency components. Typical OFC sources generate multiple optical carriers offering low power consumption and complexity by replacing multiple independent lasers with a single subsystem. Therefore, OFCs ensure constant and stable frequency spacing between the carriers enabling the reduction or elimination of guard bands in advanced multicarrier modulation techniques. In order to enable/enhance the practical use of comb sources in >100G next generation optical transport networks, a key issue to be considered is the footprint/compactness of the device as this directly relates to the ease of manufacturing (cost), power consumption, and reliability. Therefore, monolithically integrated comb sources [5, 6] with simple and compact designs could be highly beneficial. In this work, the authors present the optimum features of an integrated externally injected master slave laser [7] used to generate a gain switched optical frequency comb [8]. In addition, the employment of this comb in a flexible optical networking environment will be reviewed and experimental results presented.

Fast reconfigurable SOA-based wavelength conversion of pol-mux QPSK data employing switching tuneable pump lasers

The wavelength convertor will be a key component in future optical reconfigurable networks in order to reduce the number of power-hungry high-speed optical-electronic-optical conversions at networks nodes [1]. Even though FWM-based wavelength conversion of advanced modulation formats have already been demonstrated in [2, 3] using static, fixed-wavelength lasers; wavelength convertors with rapid, dynamic wavelength re-configurability still need to be investigated.

Polarization dependent loss due to four-wave mixing

In optical communications, four-wave mixing (FWM) is being explored for all-optical signal processing applications such as wavelength conversion. We previously demonstrated a robust scheme that was transparent to amplitude, phase and polarization of an optical signal, using a single nonlinear semiconductor optical amplifier (SOA) and two pumps with parallel polarizations [1]. We showed that it is possible to achieve polarization insensitive wavelength conversion using a single SOA by setting the detuning between the two pumps (pump-1 and pump-2), lower than that between the pumps and the signal (s), thereby achieving η<inf>1</inf> >> η<inf>2</inf>, where η: and η2 are the efficiency of the two FWM processes generating the idler frequency at ω<inf>p1</inf>–ωp<inf>2</inf> + ros [1]. Here, we show that when the detuning between the two pumps are not significantly lower than that between the pumps, FWM causes polarization dependent loss (PDL), given by, PDL (dB) = 10 log<inf>10</inf>((η<inf>1</inf>+η<inf>2</inf>)/ η<inf>1</inf>).

Novel Implementation of SOA-Based All-Optical Wavelength Conversion of DQPSK Signals Using Fast Switching Tunable Lasers

We investigate the feasibility of SOA-based wavelength conversion of DQPSK signals using wavelength tunable SGDBR pump lasers. Our results indicate that it is possible to build fast reconfigurable wavelength convertors with <5 ns switching time.

Mitigating Laser Phase Noise Induced Errors on PSK Signals Using Trellis Coding

We show how trellis coding can be employed to improve the performance of phase modulated optical transmission systems in the presence of strong phase noise.