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To answer the question: “Is optical phase conjugation (OPC) capable of compensating nonlinear distortions caused by not only Kerr effect of optical fibre, but also the carrier dynamics of semiconductor optical amplifiers (SOAs)?", we investigate the effectiveness of OPC-based nonlinear compensation for SOAs amplifying a few-channel WDM signal modulated with m-QAM. We use a pair of SOAs with an OPC stage sandwiched between the two so that the combination works as a low-distortion amplifier. Symbol-period longer than the gain recovery time is chosen in our experiments to avoid bit-pattern effects introduced by the SOA. We amplify a 12Gbaud, 16QAM modulated three-channel WDM signal with this technique in the back-to-back configuration which remarkably outperforms a single SOA in the nonlinear regime of operation with an average Q2 improvement better than 4 dB for an output power of 4 dBm. We further demonstrate the practical advantage of the low distortion higher output power capability of the SOA shown in the back-to-back result by carrying out a transmission of the amplified signal through a 160-km fibre, where relatively high launch power is desirable. We also study the case of 64QAM signals and show that approximately a 3 dB Q2 factor improvement can be obtained over single SOA, while without nonlinear phase distortion compensation, the demodulation is nearly impracticable.

We present our recent results on harnessing the nonlinear stimulated Brillouin scattering effect on a photonic chip for coherent optical communications. At the transmitter-end, an optical frequency comb was regenerated through on-chip Brillouin scattering for 64-level QAM communications. At the receiver-end, low-latency self-homodyne reception was achieved through Brillouin-assisted carrier recovery.

We demonstrate the first all-optical carrier recovery of coherent signals using on-chip Brillouin gain, replacing digital techniques, with sub-nanosecond latency. This demonstration serves as a proof-of-concept for integrated photonic carrier recovery chips for coherent communications.

We for the first time, study the effect of signal power variations on the extinction ratio and bandwidth of on-chip Brillouin filters for applications in RF photonics and coherent optical communications. The passband extinction reduces from 35 dB to 25 dB on increasing the input signal power by 36 dB, while the bandwidth increased from 13 MHz to 30 MHz.

We review waveform analysis and optical performance monitoring of ultrabroadband signals using a photonic-chip-based radio-frequency spectrum analyzer. This approach offers the potential for fast integrated monitoring and characterization of signals with bandwidths beyond 1 THz.

Progress in developing photonic chip based optical processing devices with ultrahigh-bandwidth is reviewed. The unprecedented processing bandwidth of our platform based on dispersion engineered chalcogenide waveguides is exploited to perform Tbaud optical switching and performance monitoring. Recent experiments and demonstrations of photonic logic operations are reviewed. Progress in developing photonic chip based optical processing devices with ultrahigh-bandwidth is reviewed. The unprecedented processing bandwidth of our platform based on dispersion engineered chalcogenide waveguides is exploited to perform Tbaud optical switching and performance monitoring. Recent experiments and demonstrations of photonic logic operations are reviewed

We demonstrate bit error rate improvement, corroborated by eye diagram measurements, of a (10 MHz) amplitude distorted 10 Gbit/s data signal in silicon photonic crystal waveguides. This demonstration exploits a power clamping nonlinear transfer function, provided by slow light enhancement of nonlinear absorption in these waveguides.

We present a summary of our recent experiments showing how various nonlinear phenomena are enhanced due to slow light in silicon photonic crystal waveguides. These nonlinear processes include self-phase modulation (SPM), two-photon absorption (TPA), free-carrier related effects, and third-harmonic generation, the last effect being associated with the emission of green visible light, an unexpected phenomenon in silicon. These demonstrations exploit photonic crystal waveguides engineered to support slow modes with a range of group velocities as low as c/50 and, more crucially, with significantly reduced dispersion. We discuss the potential of slow light in photonic crystals for realizing compact nonlinear devices operating at low powers. In particular, we consider the application of SPM to all-optical regeneration, and experimentally investigate an original approach, where enhanced TPA and free-carrier absorption are used for partial regeneration of a high-bit rate data stream (10 Gb/s).

Ultrahigh nonlinear tapered fiber and planar rib Chalcogenide waveguides have been developed to enable highspeed all-optical signal processing in compact, low-loss optical devices through the use of four-wave mixing (FWM) and cross-phase modulation (XPM) via the ultra fast Kerr effect. Tapering a commercial As2Se3 fiber is shown to reduce its effective core area and enhance the Kerr nonlinearity thereby enabling XPM wavelength conversion of a 40 Gb/s signal in a shorter 16-cm length device that allows a broader wavelength tuning range due to its smaller net chromatic dispersion. Progress toward photonic chip-scale devices is shown by fabricating As2S3 planar rib waveguides exhibiting nonlinearity up to 2080 W-1ldr km-1 and losses as low as 0.05 dB/cm. The material's high refractive index, ensuring more robust confinement of the optical mode, permits a more compact serpentine-shaped rib waveguide of 22.5 cm length on a 7-cm- size chip, which is successfully applied to broadband wavelength conversion of 40-80 Gb/s signals by XPM. A shorter 5-cm length planar waveguide proves most effective for all-optical time-division demultiplexing of a 160 Gb/s signal by FWM and analysis shows its length is near optimum for maximizing FWM in consideration of its dispersion and loss.

We show how slow-light enhanced four-wave mixing in dispersion engineered photonic crystal waveguides can result in ultra-compact devices enabling different applications, namely time-division demultiplexing of 160Gbaud data streams and the generation of correlated photon pairs.

We demonstrate a nonlinear signal processing approach for compensating nonlinear distortion caused by the Kerr effect in optical fiber transmission. The concept relies on propagating the signal through a separate all-optical module outside the link to apply tunable nonlinear distortion and phase-conjugation in series. We show this uniquely enables tunable regeneration of phase-encoded 40 Gb/s signals of different data-formats and number of WDM channels, to allow significantly higher transmission powers through single and multi-span fiber links. An improvement in the receiver power penalty by 3~4 dB for a bit-error-rate (BER) of ≈10−5 is achieved.

We demonstrate all-optical XOR logic function for 40Gb/s DPSK signals in the C-band, based on four-wave mixing (FWM) in a silicon nanowire. Error-free operation with a system penalty of ∼ 4.3dB at 10−9 BER has been achieved.

Nonlinear optical processes utilizing the ultrafast Kerr (χ(3)) nonlinearity provide a tool to manipulate short, picosecond long optical pulses [1], of interest for high baud rate serial communications. Increasing the nonlinear response of waveguides allows for more compact and potentially more efficient all-optical devices, with many device demonstrations in high index, highly nonlinear materials, such as silicon [2]. Further enhancing the nonlinear response of waveguides can be achieved by using resonant structures to increase the energy density, however demonstrations of signal processing using these structures have been limited to bandwidths of a few 10s of GHz at most (e.g. [3]).

We demonstrate error-free de-multiplexing of 160Gbit/s optical data to a 10Gbit/s data stream, exploiting slow light enhancement of four-wave mixing in an ultra-compact 96μm long, dispersion engineered silicon photonic crystal waveguide.

We demonstrate error-free, no power penalty, all-optical XOR operation for 40 Gbit/s phase-encoded signals in a highly-nonlinear photonic chip. This scheme exploits the Kerr nonlinearity in a dispersion-engineered chalcogenide (As 2 S 3 ) planar waveguide.

We present on-chip, all-optical pulse erasure for enabling ultrahigh-bandwidth signal processing. 15 dB pump depletion is achieved for picoseconds pulses using the instantaneous χ(3) nonlinearity in a dispersion-engineered chalcogenide waveguide.

I describe the development of highly nonlinear chalcogenide glass waveguides for photonics and their application as nonlinear optical devices for high speed processing and monitoring of telecommunications signals. Accepted version

We report the first demonstration of a photonic-chip based all-optical XOR gate for 40Gbit/s and 160Gbit/s phase-encoded signals. We achieve error-free, XOR operation for 40Gbit/s signals without power penalty in a dispersion-engineered chalcogenide waveguide.

We show that slow light is capable of enhancing nonlinear optical processes for ultra-high bandwidth all-optical signal processing on a chip at bit rates approaching 1Tb/s/. We achieve residual dispersion and optical signal to noise ratio (OSNR) monitoring via slow-light enhanced optical third-harmonic generation in dispersion engineered 2D silicon photonic crystal waveguides at bit rates from 40Gb/s to 640Gb/s.

We demonstrate residual dispersion and optical signal-to-noise ratio monitoring of optical data via slow-light enhanced third harmonic generation in dispersion engineered 2D silicon photonic crystal waveguides, at data rates up to 640Gb/s.

We report the first demonstration of all-optical Tbaud switching on a compact photonic chip. A 1.28 Tbaud return-to-zero signal was demultiplexed via four-wave mixing in a highly nonlinear, dispersion-engineered 7-cm Chalcogenide planar waveguide.

We directly investigate the influence of nonlinear loss dynamics on a slow-light silicon waveguide optical limiter, mapping how the response of free carrier absorption varies as intensity changes approach the free carrier recombination time.

We review the latest advances in dispersion-shifted, highly nonlinear planar rib waveguides fabricated in As2S3 glass for enabling broadband wavelength conversion and phase conjugation of high-speed, phase shift keyed signals via CW pumped four-wave mixing.

We demonstrate residual dispersion and OSNR monitoring from 40Gb/s to 640Gb/s via slow-light enhanced optical THG in dispersion engineered 2D silicon photonic crystal waveguides.

We report the first demonstration of optical performance monitoring of ultrahigh bit-rate phase-encoded optical signals using a cm-scale, dispersion-engineered, highly nonlinear Chalcogenide planar waveguide.

We demonstrate simultaneous monitoring of the optical signal to noise ratio (OSNR) for wavelength-division multiplexed 40 Gb/s signals using the back-reflected Stokes wave from Stimulated Brillouin Scattering. A highly sensitive OSNR range of 5-25 dB is observed.

We report all-optical in-band OSNR monitoring at 160Gb/s via slow-light enhanced third harmonic generation in a 2D silicon photonic crystal waveguide, achieving better performance than quadratic methods.

We present the first demonstration of all optical wavelength conversion in chalcogenide glass fiber including system penalty measurements at 10 Gb/s. Our device is based on singlemode As2Se3 chalcogenide glass fiber which has the highest Kerr nonlinearity (n2) of any fiber to date for which either advanced all optical signal processing functions or system penalty measurements have been demonstrated. We achieve wavelength conversion via cross phase modulation over a 10 nm wavelength range near 1550 nm with 7 ps pulses at 2.1 W peak pump power in 1 meter of fiber, achieving only 1.4 dB excess system penalty. Analysis and comparison of the fundamental fiber parameters, including nonlinear coefficient, two-photon absorption coefficient and dispersion parameter with other nonlinear glasses shows that As2Se3 based devices show considerable promise for radically integrated nonlinear signal processing devices.

We review results on the recently developed dispersion-shifted, Chalcogenide waveguides demonstrating nonlinear signal processing on a compact monolithic platform with ultra-broadband capability and moderate launch powers of around 100 mW. Highlight results include broadband wavelength conversion of high-bit rate optical signals, time division multiplexing of 320 Gb/s signals and characterization of 320 Gb/s signals using a photonic chip based RF spectrum analyzer with terahertz bandwidth. The performance advantages stem from the waveguide's design for high nonlinearity and a near zero dispersion at the 1550 nm wavelength. These features are shown to enhance the efficiency of the nonlinear processes underpinning many all-optical signal processing functions.

We demonstrate broadband wavelength conversion of a 40 Gb/s return-to-zero signal using four-wave-mixing (FWM) in a dispersion engineered chalcogenide glass waveguide. The 6 cm long planar rib waveguide 2 mum wide was fabricated in a 0.87 mum thick film etched 350nm deep to correspond to a design where waveguide dispersion offsets the material leading to near-zero dispersion in the C-band and broadband phase matched FWM. The reduced dimensions also enhance the nonlinear coefficient to 9800 W(-1)km(-1) at 1550 nm enabling broadband conversion in a shorter device. In this work, we demonstrate 80 nm wavelength conversions with 1.65 dB of power penalty at a bit-error rate of 10(-9). Spectral measurements and simulations indicate extended broadband operation is possible.

Ultra-broad bandwidth (3.75 THz) RF spectrum analysis of femtosecond optical pulses is reported for the first time, enabled by the use of a short 6 cm length Chalcogenide waveguide designed for high nonlinearity and broadband low dispersion.

We demonstrate an all-optical RF spectrum analyser with >2.5THz bandwidth based on cross-phase modulation in a dispersion-engineered, nonlinear As2S3rib waveguide.

We demonstrate use of all optical mixing in a highly nonlinear fiber to achieve microwave photonic frequency measurement. The system is simple, compact, predictable and stable with potential applications in next generation radar warning receivers.

An all-optical photonic chip RF spectrum monitor with measurement bandwidth ≫2.5 THz is reported. Using a 16 cm length, highly nonlinear and broadband low dispersive As 2 S 3 planar rib waveguide, 320 Gb/s optical signals are characterized.

A novel source of 2 ps optical pulses at 40 GHz repetition is demonstrated using a Mach-Zehnder modulator connected in a fiber-loop and compressing its output through self-phase modulation in highly nonlinear fibre and filtering.

The large, ultra-fast Kerr nonlinearity and low nonlinear loss of chalcogenide glasses are attractive for chip based all-optical signal processing. We highlight successes including optical time demultiplexing at 160 Gb/s in As2S3 planar waveguides.

A sensitive optical signal-to-noise ratio (OSNR) monitor was implemented at 160Gb/s using the non-linear power transfer function (PTF) of an asymmetrical non-linear optical loop mirror (NOLM). The device is highly sensitive in the region 5-15dB OSNR.

We present a novel principle for all-optical monitoring of optical signal-to-noise ratio (OSNR) that exploits the effect of in-band noise on stimulated Brillouin scattering (SBS). It shown for NRZ signals it can resolve OSNRs above 40 dB.

We experimentally investigate spectral phase modulation in a dynamic wavelength processor based on LCOS technology. Tunable dispersion compensation for agile optical networks is demonstrated at bitrates of 40 Gbit/s.

We establish design criteria for pump-probe devices in two photon absorbing materials and demonstrate low-power wavelength conversion over 10 nm in 1 m of single mode As/sub 2/Se/sub 3/ fiber through cross-phase modulation with only 1.4 dB system penalty at BER = 10/sup -9/.

We demonstrate all-optical wavelength conversion at 10 Gb/s for differential phase-shift keyed (DPSK) data signals in the C-band, based on four-wave mixing (FWM) in a silicon ring resonator. Error-free operation with a system penalty of ~ 4.1 dB at 10-9 BER is achieved.

We demonstrate all-optical time division demultiplexing from 160Gb/s to 10Gb/s in the C-band, based on four-wave mixing (FWM) in a silicon nanowire. We achieve error-free operation with a system penalty of approximately 3.9dB at 10(-9) BER.

The compression of higher order solitons in a standard singlemode fibre followed by a short dispersion decreasing fibre enables the high quality compression of pulses as broad as 21 ps down to 130-140 fs to be obtained from an electroabsorption modulator source over a wide modulation frequency range of 6.67-18 GHz.

We demonstrate a silicon-chip-based radio-frequency spectrum analyser capable of measuring terabaud optical data. We investigate application to optical performance monitoring and show that free-carrier effects have a negligible impact on device operation.

We demonstrate all-optical time division demultiplexing from 160Gb/s to 10Gb/s in the C-band, based on four-wave mixing (FWM) in a silicon nanowire. We achieve error-free operation with a system penalty of ∼ 3.9dB at 10–9 BER.

We investigate the nonlinear power transfer function generated through slow-light enhanced nonlinear absorption in silicon photonic crystal waveguides. Pulse regeneration and error reduction in a 10 Gbit/s data signal are observed for 10MHz amplitude distortion.

We demonstrate optical performance monitoring of in-band optical signal to noise ratio (OSNR) and residual dispersion, at bit rates of 40Gb/s, 160Gb/s and 640Gb/s, using slow-light enhanced optical third harmonic generation (THG) in a compact (80 micron) dispersion engineered 2D silicon photonic crystal waveguide. We show that there is no intrinsic degradation in the enhancement of the signal processing at 640 Gb/s relative to that at 40Gb/s, and that this device should operate well above 1Tb/s. This work represents a record 16-fold increase in processing speed for a silicon device, and opens the door for slow light to play a key role in ultra-high bandwidth telecommunications systems.

We investigate optical phase conjugation for compensating nonlinear distortions due to carrier dynamics in semiconductor optical amplifiers. Experiments with WDM-3×12 Gbaud 16-QAM signals show the ability to outperform a single device by 2 dB average Q2-factor improvement.