We have demonstrated a polarization-sensitive OFDR which uses a commercially available digital coherent optical transceiver to generate a continuous-phase linear frequency chirp by carrier-suppressed single-sideband modulation. The linearity of the digitally generated chirp was experimentally verified, confirming the suitability of the transceiver for OFDR sensing applications. A phase and polarization diverse coherent homodyne receiver recovers the state of polarization (SOP) of backscattered light using an identically chirped local oscillator. With $26\ \text{GHz}$ chirping bandwidth, a spatial resolution of approximately $5\ {\text{mm}}$ was achieved in 200 $\mu {\text{s}}$. We experimentally measured position-dependent relative magnitude and orientation of stress-induced birefringence along the fiber.

We present a thin-film barium titanate DR4 chip operating in the O-band monolithically integrated on a commercial silicon photonics platform enabling net 1.6T (4x448 Gbps PAM4) using a 3 nm CMOS SerDes.

We demonstrate improved performance using active learning for both GPR and hybrid models to predict SNR using experimental data from a 15-channel WDM system over 1000km. Physical model interpreted GPR agrees with interpreting measured data.

We present a novel measurement technique for P-OFDR with a digitally created linear chirp in the transmitter and vector complex optical field detection to measure the Stokes parameters along the fiber.

We report vibration detection and localization over a 482km bidirectional coherent optical transmission system operating error-free at 200GBd-1.6Tb/s and 200GBd-1.2Tb/s. Localization is achieved with mean offset and standard deviation of 11m and 10m, respectively.

We investigate the property of a Fabry-Perot quantum-well laser diode which emits multiple spectral lines with a total power exceeding 120mW. We show its application as an optical source in a multi-channel coherent optical system.

We demonstrate 20-channel coherent transmission using a high-power single-section QW FP-laser diode over 78.3 km single mode fiber. The system capability can reach > 4Tb/s with a single laser in the transmitter using polarizations multiplexing.

Recently several machine learning methods have been proposed to estimate the SNR, based on launch data and other system factors. These data-driven methods typically require a large number of datasets for training and generally are not interpretable. In this paper, we propose an alternative approach that requires less data and is interpretable, specifically a hybrid algorithm combining a physical model with Gaussian process regression. We develop a measurement-informed physical model, systematically reducing the number of independent parameters based on the underpinning physics and improve the overall performance of the physical model marginally. The model is validated using measurements performed on a 15-channel wavelength-division multiplexed system propagating over 1,000 km of standard single-mode fiber. The proposed hybrid model is not only interpretable but also obtains better agreement with measurements than a Gaussian process regression model and a simple neural network model for a given number of training datapoints.

With a seven-channel WDM transmission over 1000 km, we experimentally study the data-driven physics- and machine learning (ML)-based SNR estimation techniques. While the ML-based approach provides good estimation accuracy, the physics-based method performs close to it with more explainability and less training data requirements.

We experimentally demonstrate a 34 GHz integrated silicon photonic asymmetric self-coherent detection receiver enabling net 200 Gbps 16-QAM signal transmission over 40 km of SSMF below the soft decision FEC threshold.

This paper presents novel techniques to measure the total and longitudinal nonlinear phase shifts, as well as longitudinal net dispersion with a dual-polarization digital coherent transceiver in a multi-span fiber optic system. We show, with additional information of span lengths and fiber core effective areas, that the longitudinal launched power profile can be estimated. The measurement is based on cross-phase modulation between two orthogonally polarized subcarriers acting as the pump and the probe, which are generated from the same coherent transmitter. With proper waveform design in the transmitter and signal processing in the receiver, we demonstrate the feasibility of measuring the accumulated nonlinear phase shift caused by the optical signal in the fiber link between the transmitter and the receiver. Profiles of launched optical power along fiber spans can also be measured based on the differential time walk-off between the pump and the probe, and net chromatic dispersion of each fiber span along the fiber link can be estimated from this measurement. We show that digital pre-compensation on pump pulses in the transmitter and digital post-compensation on the received probe pulses are essential to ensure the accuracy of the power profile measurement.

We propose a low complexity transmitter of optical single-sideband modulation based on injection locking of a 2-section DFB laser to generate mutually-coherent tones. The scheme is experimentally demonstrated in 17-Gbd 16-QAM transmission with Kramers-Kronig reception.

We report order-of-magnitude improvements in performance of field-deployable hollow-core fiber cables evidenced by a 38.4Tb/s (800Gb/s-x-48WDM-channels) 20.5km lab-trial using commercial terminal equipment and the demonstration of 1128km/126km reach in full-fill 400/800Gb/s WDM recirculating-loop experiments.

We demonstrate a technique of evaluating optical signal to noise ratio (OSNR) associated with an optical carrier in a fiber-optic system using a commercial coherent optical transceiver equipped with digital signal processing capability. The procedure of measuring noises caused by the transmitter and the receiver is outlined, and these transceiver-related noises need to be taken into account in order to accurately evaluate the system OSNR. Through digital polarization-demultiplexing and polarization nulling in the receiver, it is possible to extract the noise underneath the optical signal, and to measure the tilt of the ASE noise spectrum within the optical signal bandwidth.

We evaluate and compare performance of three polarisation-insensitive fibre optic parametric amplifier (PI-FOP A) variants. We employ each variant to amplify a set of 21×50 GHz -spaced channels by 12.8±1.5dB and analyse bit-error rate of an amplified 100G PDM-QPSK channel as power per channel is varied. We demonstrate two variants to provide a competitive noise figure of 6 dB. We envisage each of three PI-FOPA variants to be employed for broadband communications, phase-sensitive amplification and extended-reach PON respectively.

A 12-channel single-sideband transmission of 16-QAM signals at 18 GBd is experimentally demonstrated for the first time using a single quantum-dot mode-locked laser (QD-MLL) as the light source for both the modulated carriers and the continuous wave components. The Kramers-Kronig field reconstruction algorithm was used at the direct detection receiver for signal-signal beat interference cancellation. A total net data rate of >800 Gb/s is achieved over 78 km fiber of 1680 ps/nm accumulated chromatic dispersion with BER ≤ 2 × 10 -3 , which is lower than the threshold of hard-decision FEC with 7% overhead. Numerical simulations were also performed to assess the impact of noises from the laser source and the receiver front-end on the system performance.

Perturbed spectra are modelled to estimate OSNR for a single channel amplified link. Perturbation-dependent nonlinear noise is separated from constant ASE noise using a set of propagated perturbed spectra. A least mean square fitting is used to estimate OSNR with standard deviation of 0.16 dB.

Several polarization-insensitive configurations for single-pump phase-insensitive fiber optical parametric amplifier are experimentally evaluated using 35GBaud PDM-QPSK signals. An equivalent noise figure of 9.1±1dB is experimentally derived by comparison with a variable noise figure EDFA.

The implications of cascaded optical filters on the real-time performance of a 140 Gb/s DP-QPSK transceiver are investigated by emulating passband variations through cascaded responses for both the signal and noise, and bandwidth narrowing.

We discuss the need to standardize the characterization of jitter signatures in interoperable coherent optical transceivers. Then we present test tools to determine, separately, the phase noise spectrum of transmitters and jitter tolerance of receivers.