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In this work, we firstly apply support vector machine (SVM) detector in 122-Gbps Multi-CAP system. It can de-map the rotated constellations directly without any correction. The concrete simulations indicate such a machine-learning based detector provides considerable BER reduction for high-density CAPs in low-frequency band, compared with hard decision.

We propose a novel FOCS based on polarization diversity and a real-time state of polarization (SOP) measurement to eliminate the degradation of the Faraday effect and determine the actual rotation angle of the sensing fiber.

A 32Gb/s-NRZ, 15GBaud/s-PAM4 configurable DFB Laser Diode Driver (LDD) is presented in standard 65nm CMOS. The driver employs a balanced-input, single-ended-output topology to deliver large current output, and integrates a tunable pre-emphasis to extend the bandwidth. An on-chip active back-termination (ABT) is proposed which absorbs loading reflections without sacrificing the effective modulation current. Directly wire-bonded to a DFB laser chip, the measurement results show 25.78Gb/s NRZ optical eye-diagram with 4dB Extinction Ratio (ER) and a 19.3% eye-mask margin referred to the 100G specification. The LDD delivers 60mA bias and 60mApp modulation current, consuming only 550mW power consumption.

A machine learning method of effective nonlinear decision frame for PAM-N system based on support vector machine (SVM) using complete binary tree (CBT) structure is demonstrated in this work. The simulations results indicate improved performance by the proposed classifier which enhances the power sensitivity by 2-dB and 6-dB at the receiver side in 100-Gbps PAM-4 and PAM-8 systems respectively.

In this paper, we propose and demonstrate a millimeter-resolution long-range optical frequency domain reflectometry (OFDR) using an ultra-linearly 100-GHz swept optical source realized by injection-locking technique and cascaded four-wave-mixing (FWM) process. The ultra-linear sweep is realized using an external modulation method with a linearly swept radio frequency (RF) signal. The RF signal sweeps from 16 GHz to 19.3 GHz, and the slave laser is injection-locked to the 8th-order sideband of the master laser, achieving a frequency sweeping span of ~25 GHz. By using the injection-locked frequency-swept laser as the optical source of OFDR, we obtain a spatial resolution of 4.2 mm over 10-km measurement range. A polarization beat length of 10.5 cm is measured benefiting from the high spatial resolution. To improve the spatial resolution further, FWM process is used to broaden the frequency sweeping span. Frequency sweeping span of ~100 GHz is achieved with cascaded FWM. We demonstrate a 1.1-mm spatial resolution over 2-km measurement range with the proposed ultra-linearly swept optical source.

We present the epitaxial growth of materials, wafer-level device fabrication and characterization of mass-production 200-Gb/s 850nm 1 ×4 VCSEL array with maximum current-light slope efficiency up to 1.03 W/A, operating at 25-Gb/s OOK and 50-Gb/s PAM4.

In this paper, probabilistic shaping for PAM-4 signalling at 56 Gbps is demonstrated for the first time. Experiment is carried out over 8-GHz-bandwidth VCSEL-modulated optical interconnection links with significantly reduced BER due to probabilistic shaping.

We experimentally demonstrate, for the first time to our best knowledge, an ultra-low- noise second-order few-mode Raman amplified 8-λ WDM/MDM QPSK transmission over 100-km FMF with ∼8-dB on-off gain and 01 and LP 11 modes.

We first experimentally demonstrate a second-order few-mode distributed Raman amplifier with 4 dB mode-equalized gain. The noise figure improvement of the LP 01 and LP 11 modes are respectively 1.1 dB and 0.9 dB compared with first-order Raman amplification scheme.

We propose a novel optical computing architecture for massive parallel matrix manipulation based on reconfigurable time-wavelength plane manipulation and and dispersed time delay. Two linear weighting methods in either wavelength or time domain are proposed and validated. We perform the autocorrelation function of a 7-bit m-sequence with the speed at 1.18×1011 multiplications and accumulations per second (MACs/s) and a multiplication of a 4 × 4 matrix and a 4 × 1 vector at 2.69×109 MACs/s. The edge extraction of 32 × 32 binary images is also realized in simulation by optical 2D convolution at 5×108 MACs/s. The proposed optical computing unit can be a key building block to process complex computing tasks with advanced deep learning algorithms and it is promising for the future photonic neural network circuits.

With cascaded and multisection Sagnac interferometers, all-optical fast Fourier transform (FFT) has been demonstrated for optical demultiplexing (DEMUX) of orthogonal frequency division multiplexing (OFDM) signals. The transmission characteristics of the interferometers have been investigated theoretically and experimentally. The scalability and tunability of the all-optical OFDM DEMUX are analyzed and demonstrated for 5-channel OFDM signals.

In this work, 4-level pulse amplitude modulation (PAM4) by using commercial dual-drive Mach-Zehnder Modulator (DD-MZM) is experimentally investigated. We have demonstrated the generation of PAM4 signal up to 50 Gbaud (100 Gbps). The transmission of the PAM4 signal over 5-Km standard single mode fiber (SSMF) is achieved with error-free below the FEC limit (3.8E-3), without employing digital equalization at 90 Gbps. The linear-amplifier-free configuration by DD-MZM leads to simplified implementation and improved performance for high speed PAM4 signal generation, which would be of great significance for short reach optical interconnection.

Multi-dimensional carrierless amplitude phase (CAP) modulation attracts a lot interest in recent optical communications as an advanced modulation format with improved performance. In this study, we have demonstrated a multiband multi-dimensional CAP modulation scheme and investigated its applications in short reach optical communication systems. Similar to discrete multitone (DMT) technique, several independent bands can be loaded with different three dimensional carrierless amplitude phase (3D-CAP) signals in the proposed multiband 3-dimensional CAP system, offering improved tolerance to non-flat channels. Experimental transmission of 3D-CAP over SMF up to 45Gbps is also demonstrated.

We demonstrate the design of an orientation-insensitive mode-selective coupler working as a DeMUX for two-mode transmission at 850 nm using SSMF. The mode extinction ratios of LP01/LP11 and LP11/LP01 are above 12.6 dB and 21.2 dB in the band of 845 to 855 nm.

We designed and fabricated low loss polymer waveguides (

We experimentally demonstrate the transmission of 30-Gbit/s three-dimensional carrierless-amplitude-phase modulation (3D-CAP) signals over 12-km single mode fiber (SMF) using bandwidth-limited devices. To our best acknowledge, this is the highest speed transmission of 3D-CAP with fiber distance over 10 km.

A single-chip Optical Time Domain Reflectometer (OTDR) system-on-chip (SoC) for fiber-optic fault detection and localization is presented. The IC can be configured into several modes including high-performance mode (external modulator and expensive off-chip laser / APD), and low-cost mode (low power/gain and inexpensive laser / APD). Experimental optical measurements demonstrate that the maximum detectable fiber length of the proposed OTDR SoC can be as long as 25km, while the spatial resolution can achieve 2.5m, 4m and 10m, for various configurations. Compared with current discrete solutions on the market, the proposed OTDR system can reduce the cost by 100x, area by 5x, and power consumption by 4x.

We experimentally demonstrate a 56-Gb/s PAM-4 transmission over 5-km SSMF using photonic digital-to-analog converter based on polarization multiplexing. The performance of optical PAM-4 generator is analyzed and compared with electrical counterpart.

We propose a novel fiber optic current sensor with high sensitivity and reconfigurable operation capability based on recirculating-loop configuration using standard SMF. We achieved a sensitivity as high as 42.6 degrees per ampere.

We demonstrate a high spatial resolution optical coherence domain reflectometry with synthesis of coherence function by using high-order degenerated four-wave-mixing process. A 1.9-mm spatial resolution is realized with the second-order idler as a light source.

We demonstrate a high spatial resolution OFDR by utilizing injection-locking technique and cascaded FWM. A frequency sweeping span of ~100 GHz is obtained for realizing a 1.1 mm spatial resolution over 2 km measurement range.

We theoretically studied the mode coupling between two identical weakly-coupled few-mode fibers. By carefully choosing the fiber core separation and coupler length, we successfully designed orientation-insensitive fiber couplers for non-circular-symmetric modes with arbitrary coupling ratios.

In this study, for the first time, we experimentally demonstrated the machine learning method of K-nearest neighbour (K-NN) algorithm to mitigate nonlinear constellation distortion in optical carrier-less amplitude phase modulation (CAP) system.

We experimentally demonstrate a 100-Gbps optically-uncompensated PAM-4 transmission over 4-km SSMF at 1.55-um by using Wiener filter. The performance of the adaptive filters, including LMS and Wiener filter, are both analysed and compared.

We propose novel ring-assisted 7-LP-mode fiber with ultra-low inter-mode crosstalk without obvious degradation on other characteristics by improving the minimum value of $\Delta \mathrm{n}_{\text{eff}}$ for 70%. We experimentally verified feasibility of our method in 4-LP-mode fiber.

We design and experimentally demonstrate a few-mode Raman amplifier over the C+L band with a flat on-off gain of ∼4 dB, for the first time, to the best of our knowledge. A state-of-the-art gain bandwidth of 75 nm (1530–1605 nm) is achieved. The wavelength-dependent gain for both LP01 and LP11 modes is about 0.6 dB, and the maximum mode-dependent gain is less than 0.3 dB. Mode-division multiplexed optical transmissions are performed over 75 km few-mode fiber assisted by the proposed Raman amplifier. Due to the low noise Raman amplification, more than 3.3 dB optical signal-to-noise ratio enhancement has been obtained with a significantly improved bit-error rate of about two orders.

A stable and narrow wavelength spacing multiwavelength erbium-doped fiber laser is proposed and demonstrated. The laser can produce simultaneous dual- and triple-wavelength lasing oscillations with a narrow wavelength spacing of less than 0.1 nm via using a single fiber Bragg gratings written in polarization-maintaining (PM) fiber. By adjusting polarization controller, the wavelength spacing of dual-wavelength lasing oscillations can be tuned to as small as 0.032 nm. The maximum amplitude variation for every lasing wavelength is less than 0.5 dB. The room-temperature operation principle is based on the polarization hole burning and deeply saturated effect in an ordinary erbium-doped fiber ring laser (EDFRL). The laser has the advantages of simple all-fiber configuration, low cost, high stability and operating at room temperature.

We propose and demonstrate a stable room-temperature channel-spacing and wavelength switchable multiwavelength erbium-doped fiber (EDF) laser using a sampled Hi-Bi fiber grating and a photonic crystal fiber (PCF) loop mirror. The PCF loop mirror induces the intensity-dependent cavity loss to suppress the wavelength competition of the EDF. By adjusting the polarization controller, we can achieve 0.4 nm and 0.8 nm channel-spacing of the multiwavelength EDF laser. The measured power fluctuation of each wavelength is less than 0.2 dB and the peak power differences among the main oscillation wavelengths are less than 1.0 dB. Another desirable characteristic is that it needs a relatively low pump power of 100 mW.

We present a newly developed high performance fiber optics sensor for quasi-static strain measurement. The sensor consists of a piece of π-phase shifted FBG for static strain sensing, and fiber Fabry-Perot interferometer for reference, interrogated by an improved sideband interrogation method with real-time feedback loops. Strain resolution of 0.12 nano-strain was achieved with sampling rate up to 1 kS/s in laboratory experiments. Compared with previous sensor systems, the proposed method shows great improvement in the sensing rate as well as the resolution.

We demonstrated the use of optical signal processing to enhance the performance of optical fiber sensors, including FBG sensor and OFDR. Regarding FBG sensors, FWM in a HNLF to enhance the sensitivity of a fiber sensor is demonstrated based on frequency chirp magnification. Meanwhile, OFDR with improved spatial resolution is realized assisted by high power modulation, FWM and RFS. The use of the all-optical signal processing opens a new window for advanced fiber optic sensing. Since the method only processes the signal and thus it can be applied to a wide range of sensors without changing the sensor itself.

We reported an optical fiber based temperature sensor with mK-order resolution, wide temperature range and excellent long term stability. The sensor composes of a fiber Bragg grating (FBG) as the sensing element, an HCN gas cell for absolute frequency reference. A distributed feedback diode laser with current modulation is used as the light source. To overcome the frequency-sweep nonlinearity of the laser, an auxiliary Fabry-Perot interferometer with free spectrum range of 10 MHz is employed. A cross-correlation algorithm is employed to calculate the center frequency difference between the FBG and the gas cell. With the proposed configuration, a temperature resolution of 0.41 mK was demonstrated in experiment. To the best knowledge, this is the first time that an mK order temperature resolution has been achieved by optical fiber sensor.

We developed a novel optical coherent domain reflectometer (OCDR) technique with large measurement range by using of dual frequency modulation. The probe and local oscillator beams are frequency modulated independently, and the sensing position can be adjusted digitally via the time delay between the driving signals for the two modulators. Meanwhile, the frequency tuning spans of the two paths are different to enable heterodyne detection. In the demonstrational experiments, a spatial resolution of 3.9 m over a range of 24.6 km fiber was achieved with 35 MHz tunable range of the modulator, and the spatial resolution keeps a constant over the whole measurement range.

We demonstrate a novel method for obtaining high spatial resolution optical frequency domain reflectometry (OFDR) utilizing recirculating frequency shifter for broadening the optical frequency sweeping. 10-times broadened optical frequency sweeping is achieved. 1.46-cm spatial resolution is obtained with modulation frequency sweeping span of 712 MHz.

A digitally enhanced optical frequency domain reflectometry technique is proposed, in which the frequency-to-distance mapping is realized in digital domain. A spatial resolution of 1 m over 56 km was obtained in demonstrational experiments.

A method for enhancing the sensitivity of a fibre Bragg grating (FBG) sensor by all-optical signal processing is demonstrated. Degenerated four-wave mixing (FWM) has been used to perform frequency chirp magnification, which can be used for magnifying the wavelength drift of the FBG sensor. Ultra-highly sensitive measurement of the static strain has been experimentally demonstrated with strain sensitivity of 5.40 pm/μɛ. The sensitivity has been enhanced by a factor of five.

An efficient optical comb generation method based on degenerated four-wave-mixing process in highly nonlinear fibre is demonstrated. The all-optical processing of the frequency chirp is wavelength tunable and thus enables the capability of tunable chirp magnification. The magnification of the frequency chirp with a factor tunable from two to five has been demonstrated. An optical comb with 22 sub-carriers has been obtained which refers to a bandwidth of 210 GHz, about five times the bandwidth of 40 GHz for the original signal.

We report the relative intensity noise (RIN) characteristics of an InAs quantum dot (Qdot) laser epitaxially grown on the Ge substrate. It is found that the minimum RIN of the Ge-based Qdot laser is around −120 dB/Hz, which is 15 dB higher than that of a native GaAs-based Qdot laser with the same layer structure. The higher RIN in the Ge-based laser can be attributed to the high-density epitaxial defects of threading dislocations and antiphase domain boundaries.

10 Gbit/s 1×4 wavelength multicasting of a DPSK signal with NRZ-to-RZ format conversion is demonstrated. The operation is achieved by four-wave mixing of the input DPSK signal with a time- and wavelength-interleaved pulsed source. Four multicast channels have been achieved with error-free operation.

We perform all-optical return-to-zero (RZ) to nonreturn-to-zero (NRZ) and NRZ to pseudoreturn-to-zero (PRZ) format conversions at tunable bit rates, both by using the same delay-asymmetric nonlinear loop mirror. The temporal and spectral characteristics of the input and output signals are analyzed. Bit-error-rate measurements of RZ-to-NRZ conversion at 10 and 12.5 Gb/s show error-free performance with power penalties less than 3 dB with reference to the input RZ signals.

We demonstrate a method for high spatial resolution optical frequency domain reflectometry (OFDR) by utilizing degenerated four-wave-mixing (FWM) for broadening the frequency sweeping. High order sideband is obtained from an optical comb and is consequently utilized as the pump for the FWM. An idler wavelength is produced after the FWM and 21-times broadened optical frequency sweeping is achieved compared with the radio frequency (RF) sweeping. 0.75-cm spatial resolution is obtained with RF frequency sweeping span of 638.4 MHz.

Advances in optical reflectometry, including a novel OCDR using an optical frequency comb source, a high spatial resolution OFDR based on broadened frequency sweeping by four-wave-mixing, and coherent-OTDRs, are reviewed. Article not available.

Optical parametric amplification (OPA) and high-order four-wave-mixing (FWM) are utilized for enhancing the strain and temperature sensitivity of an FBG sensor. Record performance of BJ-pm/°C strain sensitivity and 141.2-pm/°C temperature sensitivity are obtained.

A high sensitivity electric field optical fiber sensor was reported for the measurement of strong electric field, avoiding the impact on the electric field and the risk of electric shock.

We describe a prototype development of phase-sensitive coherent optical time domain reflectometry (φ-COTDR), which is used for distributed vibration measurement. It has a frequency response of 200 Hz with a measurement range of 40 km.

A novel optical reflectometry technique capable of suppressing the influence of phase noise is developed. A spatial resolution of 2 m over 55 km range was experimentally demonstrated with a DFB laser.

Ultra-fast optical ultrawideband (UWB) pulse generation is demonstrated based on cross phase modulation in a dispersion-asymmetric nonlinear optical loop mirror (DA-NOLM). High speed UWB monocycle pulses with tunable control of the polarities have been obtained.

We propose and demonstrate a tunable multiwavelength erbium-doped fiber laser based on a polarization-maintaining photonic crystal fiber (PM-PCF) Sagnac loop filter. Stable, room-temperature operation is obtained by employing a nonlinear optical loop mirror. At a central wavelength of 1563.000 nm, we generate 60 wavelengths within 3-dB bandwidth. The measured power fluctuation for each lasing wavelength is less than 0.2 dB in half an hour. Furthermore, by adjusting the polarization controllers in the Sagnac filter, wavelength locations of the laser lines with a fixed channel spacing of ∼ 0.078 nm can be continuously shifted.

We propose a novel design of all-solid photonic bandgap fiber (AS-PBGF). It is designed by introducing a new defect, several bigger high-index rods, in the cladding of a conventional AS-PBGF. Using the plane-wave expansion method and the full-vector finite-element method, we study the effect of introducing such bigger high-index rods. The numerical results show that both large normal and anomalous dispersion are induced within bandgap rather than near the edge of bandgap as conventional PBGF does. More importantly, the confinement loss of the LP01 modes around the wavelengths, where large normal and anomalous dispersion are induced, could be decreased by increasing the rings of high-index rods for the fact that these wavelengths are within the bandgap.

We utilize frequency chirp magnification for enhancing the strain sensitivity of an FBG sensor. Ultra-highly sensitive strain measurement has been achieved with 5.40 pm/μϵ strain sensitivity, which has been enhanced by a factor of five.