Ambient noise-based weakly supervised manhole localization methods over deployed fiber networks.

We present a manhole localization method based on distributed fiber optic sensing and weakly supervised machine learning techniques. For the first time to our knowledge, ambient environment data is used for underground cable mapping with the promise of enhancing operational efficiency and reducing field work. To effectively accommodate the weak informativeness of ambient data, a selective data sampling scheme and an attention-based deep multiple instance classification model are adopted, which only requires weakly annotated data. The proposed approach is validated on field data collected by a fiber sensing system over multiple existing fiber networks.

Optical-Amplifier-Compatible Long-Distance Secure Key Generation Based on Random Phase Fluctuations for WDM Systems.

We proposed and experimentally demonstrated a secure key generation and distribution system that is compatible with optical amplifiers and standard wavelength-division multiplexing (WDM) transmission systems. The key is generated from the phase fluctuations induced by environmental instabilities. The key generation system is tested in a 240 km bidirectional fiber-pair link with multiple optical amplifiers. To demonstrate the compatibility with WDM systems, 38 WDM channels are transmitted together with the key distribution channel. The secret key is protected against eavesdropping and coherence detection attack by the wide-band property of the signal carrier and the fast-changing rate of the phase fluctuations.

Multi-parameter distributed fiber sensing with higher-order optical and acoustic modes.

We propose a novel multi-parameter sensing technique based on a Brillouin optical time domain reflectometry in the elliptical-core few-mode fiber, using higher-order optical and acoustic modes. Multiple Brillouin peaks are observed for the backscattering of both the LP01 mode and LP11 mode. We characterize the temperature and strain coefficients for various optical-acoustic mode pairs. By selecting the proper combination of modes pairs, the performance of multi-parameter sensing can be optimized. Distributed sensing of temperature and strain is demonstrated over a 0.5-km elliptical-core few-mode fiber, with the discriminative uncertainty of 0.28°C and 5.81 µÎµ for temperature and strain, respectively.

Discrimination of Temperature and Strain in Brillouin Optical Time Domain Analysis Using a Multicore Optical Fiber.

Brillouin optical time domain analysis is the sensing of temperature and strain changes along an optical fiber by measuring the frequency shift changes of Brillouin backscattering. Because frequency shift changes are a linear combination of temperature and strain changes, their discrimination is a challenge. Here, a multicore optical fiber that has two cores is fabricated. The differences between the cores' temperature and strain coefficients are such that temperature (strain) changes can be discriminated with error amplification factors of 4.57 °C/MHz (69.11 µ ϵ /MHz), which is 2.63 (3.67) times lower than previously demonstrated. As proof of principle, using the multicore optical fiber and a commercial Brillouin optical time domain analyzer, the temperature (strain) changes of a thermally expanding metal cylinder are discriminated with an error of 0.24% (3.7%).

Demonstration of digital phase-sensitive boosting to extend signal reach for long-haul WDM systems using optical phase-conjugated copy.

We demonstrate a hybrid optical/digital phase-sensitive boosting (PSB) technique for long-haul wavelength division multiplexing (WDM) transmission systems. The approach uses four-wave mixing (FWM) to generate a phase-conjugated idler alongside the original signal. At the receiver, the signal and idler are jointly detected, and the phases of the idler symbols are conjugated and summed with the signal symbols to suppress noise and nonlinear phase distortion. The proposed hybrid PSB scheme is independent of modulation format and does not require an optical phase-locked loop to achieve phase matching required by conventional phase-sensitive amplifiers. Our simulation and experimental results of 112-Gb/s dual-polarization quadrature phase-shift-keying (DP-QPSK) transmission confirmed the principle of the PSB scheme, attaining a Q-factor improvement of 2.4 dB over conventional single-channel transmission after 4,800 km of dispersion-managed fiber (DMF) link at the expense of 50% reduction in spectral efficiency and extending the system reach by 60% to 7,680 km.

30Tb/s C- and L-bands bidirectional transmission over 10,181km with 121km span length.

We demonstrated the first 30Tb/s (350 × 85.74Gb/s) optical transmission over 10,181km using bidirectional C/L-bands, 121.2km hybrid fiber spans, DP-QPSK modulation and EDFAs. Achieved 306Petabit/s•km capacity × distance product is the highest reported to date for WDM transmission.

Mode-division multiplexed transmission with inline few-mode fiber amplifier.

We demonstrate mode-division multiplexed WDM transmission over 50-km of few-mode fiber using the fiber's LP01 and two degenerate LP11 modes. A few-mode EDFA is used to boost the power of the output signal before a few-mode coherent receiver. A 6×6 time-domain MIMO equalizer is used to recover the transmitted data. We also experimentally characterize the 50-km few-mode fiber and the few-mode EDFA.

Optical FFT/IFFT circuit realization using arrayed waveguide gratings and the applications in all-optical OFDM system.

Arrayed waveguide gratings (AWG) are widely used as wavelength division multiplexers (MUX) and demultiplexers (DEMUX) in optical networks. Here we propose and demonstrate that conventional AWGs can also be used as integrated spectral filters to realize a Fast Fourier transform (FFT) and its inverse form (IFFT). More specifically, we point out that the wavelength selection conditions of AWGs when used as wavelength MUX/DEMUX also enable them to perform FFT/IFFT functions. Therefore, previous research on AWGs can now be applied to optical FFT/IFFT circuit design. Compared with other FFT/IFFT optical circuits, AWGs have less structural complexity, especially for a large number of inputs and outputs. As an important application, AWGs can be used in optical OFDM systems. We propose an all-optical OFDM system with AWGs and demonstrate the simulation results. Overall, the AWG provides a feasible solution for all-optical OFDM systems, especially with a large number of optical subcarriers.

1.92 Tb/s coherent DWDM-OFDMA-PON with no high-speed ONU-side electronics over 100 km SSMF and 1:64 passive split.

Record 1.92-Tb/s (40λ × 48 Gb/s/λ) coherent DWDM-OFDMA-PON without high-speed ONU-side ADCs/DACs/DSP/RF clock sources is demonstrated over 100 km straight SSMF with a 1:64 passive split. Novel optical-domain OFDMA sub-band selection, coherent detection, and simple RF components are exploited. As the first experimental verification of a next-generation optical platform capable of delivering 1 Gb/s to 1000(+) users over 100 km, the new architecture is promising for future optical access/metro systems.

Single integrated device for optical CDMA code processing in dual-code environment.

We report on the design, fabrication and performance of a matching integrated optical CDMA encoder-decoder pair based on holographic Bragg reflector technology. Simultaneous encoding/decoding operation of two multiple wavelength-hopping time-spreading codes was successfully demonstrated and shown to support two error-free OCDMA links at OC-24. A double-pass scheme was employed in the devices to enable the use of longer code length.

Simultaneous all-optical 3R regeneration scheme with improved scalability using TOAD.

A novel re-timing, re-amplifying, and re-shaping (3R) regeneration system is proposed to process multiple WDM (wavelengthdivision-multiplexing) channels simultaneously. Its re-timing capability is investigated by both simulation and experiment with polarizationscrambling method at 10 Gb/s bit rate. Jitter tolerance up to 0.8 UIpp is demonstrated with BER improvement and floor breaking ability.

All-optical 160 Gbits/s time-domain demultiplexer based on the heavily GeO2-doped silica-based nonlinear fiber.

We present a nonlinear optical loop mirror (NOLM)-based 160 Gbits/s demultiplexer built with a new generation of silica-based nonlinear fibers. Together with the record-breaking length of only 11 m, the demonstrated NOLM has a relatively low control signal power, which is comparable to the best results for bismuth-oxide fibers to date, resulting in a four-times smaller power-length product than any previous silica fiber. Further, unlike previous silica-based approaches, the demonstrated demultiplexer does not require any dispersion management because of its extremely short length. The device is operable with a randomized input polarization at a bit error rate of 10(-8).