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This work presents a wide-area highway monitoring system based on distributed fiber-optic sensing (DFOS) as a cost-effective way of gathering traffic information at numerous sensing points along a fiber cable. The primary advantage of our proposed DFOS system is that it utilizes an existing fiber cable buried beneath the highway to detect and localize the vibrations of passing vehicles. Each section along the fiber cable acts as a sensing point and registers the vibration of nearby vehicles. The amplitude and location of vibrations as measured by DFOS can supplement the information obtained from existing point sensor systems (traffic camera, inductive loop detector) which are typically installed hundreds of meters apart. We trained a neural network for speed estimation ( SpeedNet) and also proposed novel solutions to some of the challenges posed when using DFOS to monitor traffic. To demonstrate the potential of DFOS, we conducted a field test for two days on a 45-km section of the Tomei expressway in Japan. Our proposed SpeedNet model estimated average traffic speeds every minute for an overall accuracy of over 90% as compared with existing loop detector-based sensors. As cameras suffer from weather and intensity changes, and loop detectors can be difficult to install at multiple locations, monitoring traffic using DFOS over an existing fiber-optic cable shows tremendous potential.

We review the distributed-fiber-sensing field trial results over deployed telecom networks. With local AI processing, real-time detection, and localization of abnormal events with cable damage threat assessment are realized for cable self-protection.

We report field test results of facility perimeter intrusion detection with distributed-fiber-sensing technology and backscattering-enhanced-fiber by using deployed telecom fiber cables as sensing backhaul. Various intrusive activities, such as walking/jumping at >100ft distance, are detected.

We review sensing fusion results of integrating fiber sensing with video for machine-learning-based localization and classification of impulsive acoustic event detection. Classification accuracy >97% was achieved on aerial coils, and >99% using fiber-based signal enhancers.

We report the first distributed acoustic sensing (DAS) results over >1,000 km on a field-lab hybrid link using chirped-pulses with correlation detection and 20× frequency-diversity, achieving a sensitivity of 100 p ∈ / Hz at 20-meters spatial resolution.

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.

To the best of our knowledge, we present the first field trial of distributed fiber optical sensing (DFOS) and high-speed communication, comprising a coexisting system, over an operation telecom network. Using probabilistic-shaped (PS) DP-144QAM, a 36.8 Tb/s with an 8.28-b/s/Hz spectral efficiency (SE) (48-Gbaud channels, 50-GHz channel spacing) was achieved. Employing DFOS technology, road traffic, i.e., vehicle speed and vehicle density, were sensed with 98.5% and 94.5% accuracies, respectively, as compared to video analytics. Additionally, road conditions, i.e., roughness level was sensed with >85% accuracy via a machine learning based classifier.

We demonstrate a new application of fiber-optic-sensing and machine learning techniques for vehicle run-off-road events detection to enhance roadway safety and efficiency. The proposed approach achieves high accuracy in a testbed under various experimental conditions.

We report the field trial results of monitoring abnormal activities near deployed cable with fiber-optic-sensing technology for cable protection. Detection and position determination of abnormal events and evaluating the threat to the cable is realized.

We report the distributed-fiber-sensing field trial results over a 5G-transport-network. A standard communication fiber is used with real-time AI processing for cable self-protection, cable- cut threat assessment and road traffic monitoring in a long-term continuous test.

Distributed fiber optical systems (DFOS) allow deployed optical cables to monitor the ambient environment over wide geographic area. We review recent field trial results, and show how DFOS can be made compatible with passive optical networks (PONs).

We demonstrate vibration detection and localization based on extracting optical phase from the DSP elements of a coherent receiver in bidirectional WDM transmission of 200-Gb/s DP-16QAM over 380 km of installed field fiber.

We demonstrate fiber optic sensing systems in a distributed fiber sensor network built on existing telecom infrastructure to detect temperature, acoustic effects, vehicle traffic, etc. Measurements are also demonstrated with different network topologies and simultaneously sensing four fiber routes with one system.

To the best of our knowledge, we present the first underground fiber cable position detection methods using distributed fiber optic sensing (DFOS) technology. Meter level localization accuracy is achieved in the results.

Distributed fiber optic sensing (DFOS) is a rapidly evolving field that allows the existing optical fiber infrastructure for telecommunications to be reused for wide-area sensing. Using the backscattering mechanisms of glass—which includes Rayleigh, Brillouin, and Raman backscatter—it is possible to realize distributed vibration and temperature sensors with good sensitivity at every fiber position, and spatial resolution is determined by the bandwidth of the interrogation signal. In this paper, we will review the main technologies in currently deployed DFOS. We review the digital signal processing operations that are performed to extract the sensing parameters of interest. We report recent distributed vibration sensing, distributed acoustic sensing, and distributed temperature sensing field trial results over an existing network with reconfigurable add/drop multiplexers carrying live telecom traffic, showing that the network is capable of simultaneous traffic and temperature monitoring. We report Brillouin optical time-domain reflectometry experimental results for monitoring static strain on aerial fiber cables suspended on utility poles. Finally, we demonstrate an example of network modification to make passive optical networks compatible with DFOS by adding reflective semiconductor optical amplifiers at optical network units.

We demonstrated for the first time that geographic locations on deployed fiber cables can be determined accurately by using OTDR distances. The method involves vibration stimulation near deployed cables and distributed fiber optical sensing technology.

We proposed and demonstrated a new machine learning algorithm for wavelength modulation spectroscopy to enhance the accuracy of fire detection. The result shows more than 8% of accuracy improvement by analyzing CO/CO 2 2f signals.

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 back scattering 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 με for temperature and strain, respectively Refereed/Peer-reviewed

For the first time, we demonstrate detection of vehicle speed, density, and road conditions using deployed fiber carrying high-speed data transmission, and prove carriers' large-scale fiber infrastructures can also be used as ubiquitous sensing networks.

Angiopoietin-like protein 2 (Angptl2) is regarded as a proinflammatory factor in the pathogenesis of atherosclerosis and is expressed at high levels in patients with coronary artery disease. However, direct evidence of Angptl2 in acute coronary syndrome (ACS) is lacking. Our study was designed to investigate a possible relationship between serum Angptl2 and ACS.We evaluated 251 consecutive patients undergoing coronary angiography, consisting of 132 patients with ACS (unstable angina pectoris n = 60, acute myocardial infarction n = 72), 50 patients with stable angina pectoris, and 69 control patients. Serum Angptl2 concentration was measured in peripheral venous blood by an enzyme-linked immunosorbent assay.Serum Angptl2 levels were significant higher in patients with ACS than in those with stable angina (p0.05) or controls (p0.001). The difference between angplt2 levels in unstable angina and acute myocardial infarction subgroups was statistically insignificant (p = 0.831). In multivariable logistic regression models, using quartiles of Angptl2, Angptl2 was closely associated with ACS following adjustment of age, gender, established risk factors and high sensitivity C-reactive protein levels (odds ratio for quartile 4 vs. quartile 1: 10.182, 95% confidence interval 2.440-42.485, p = 0.001).Serum Angptl2 is a new candidate biomarker for risk stratification of ACS.

We propose a single-ended Brillouin-based sensor in elliptical-core few-mode optical fiber for multi-parameter measurement using spontaneousBrillouin scattering. Distributed sensing of temperature and strain is demonstrated over 0.5 km elliptical-core few-mode fiber. Refereed/Peer-reviewed

In this paper, we propose and experimentally verify a low-latency digital signal processing (DSP)-free synchronous clock distribution and recovery scheme for high-speed dense wavelength division multiplexing orthogonal frequency division multiple access (DWDM-OFDMA)-based mobile backhaul (MBH) systems. The synchronous clock distribution is achieved jointly with high-speed OFDMA data signal transmission through a simple and low-cost intensity-modulation direct-detection (IMDD) optical backhaul architecture that also guarantees clock time and frequency stability. We experimentally verify aggregate 41.09-Gb/s (7λ × 5.87 Gb/s/λ) DWDM-OFDMA data rates with distribution and recovery of 50-MHz square wave and 4-GHz sinusoid clocks over 40 km standard single mode fiber (SSMF) with spectrally-efficient 25-GHz channel spacing and no remote optical amplification. To demonstrate the flexibility of the proposed system, aggregate 51.31-Gb/s (7λ × 7.33 Gb/s/λ) DWDM-OFDMA transmission with 50-MHz square wave and 5-GHz sine wave clocks is also experimentally evaluated. Highly precise time and frequency accuracy is achieved, featuring an order of magnitude improvement with respect to LTE-Advanced (LTE-A) synchronization requirements. By supporting high bit rates, high spectral efficiency, and low-latency synchronization, the proposed approach is promising for future optical MBH.

We report the results of two field trials aimed at achieving high fiber capacity over regional and long-haul distances. In the first trial, 41 superchannels with digital Nyquist pulse-shaping were generated and tightly packed to fill up both C-band and L-band. Each subcarrier was modulated with 24.8-Gbaud dual-polarization 16 quadrature amplitude modulation (DP-16QAM) data. The signal carrying net 54.2 Tb/s data was transmitted over 634 km of dispersion uncompensated field-installed standard single mode fiber with the aid of hybrid EDFA and Raman amplification and digital coherent detection. In the second trial for long-haul distances, we extended the transmission distance over 1,822 km. This increase in reach was achieved by reducing the net total capacity to 40.5 Tb/s and modulating the signals with dual-polarization 8 quadrature amplitude modulation (DP-8QAM) Nyquist carrier modulation. A novel rate-adaptive low-density parity-check coding was employed, so that the transmitted channels can exhibit different code rates, adapted by the concatenation of hard-decision and soft-decision forward error correcting codes for enhancing error-correction capability. To the best of our knowledge, we achieved the highest field trial capacity to date at 54.2 Tb/s in regional distances. Furthermore, in long-haul applications, the reported capacity × distance product of 73.79 Pb/s·km is the highest to date.

We report the results of two separate field trials aimed to achieve high fiber capacity over long-haul distances. In the first trial, 22 all-optical orthogonal frequency-division multiplexing superchannels with hybrid dual-polarization 8 quadrature amplitude modulation and dual-polarization quadrature phase-shift-keying (DP-QPSK) modulation were generated using a novel flexible format superchannel transmitter design. The signal carrying net 21.7 Tb/s data was transmitted over 1503 km of dispersion uncompensated field-installed standard single-mode fiber with the aid of hybrid Raman and erbium-doped fiber amplifier (EDFA) amplification and digital coherent detection. In the second trial, we extended the transmission distance to over 2531 km of field fiber using only EDFA for loss compensation. The increase in reach was achieved by reducing the net total data rate to 16.2 Tb/s and modulating the optical superchannel subcarriers with DP-QPSK only. To the best of our knowledge, we achieved the highest capacity field trial record to date at 21.7 Tb/s in the first trial, while the achieved capacity-distance product of 40.9 Pb/s ·km in the second trial is also the highest reported to date.

We experimentally demonstrated transmitting 40 × 117.6 Gb/s 16 quadrature amplitude modulation with orthogonal frequency division multiplexing modulation over 10 181 km. The following techniques are applied to achieve error-free transmission: 1) hybrid large-core/ultralow-loss fibers were used for improving received optical signal-to-noise ratio while enhancing fiber nonlinearity tolerance; 2) multiband nonlinearity compensation algorithm was performed to further improve nonlinearity tolerance; 3) the forward error correction (FEC) limit of 5.3 dB provided by the concatenation of hard-decision and soft-decision FEC codes ensures to have error-free transmission after turbo equalizer with memory of three symbols, thus attaining a spectral efficiency of 4.7 b/s/Hz.

We experimentally demonstrate 101.7-Tb/s transmission over 355 km spans of standard single-mode fiber (SSMF) at a net spectral efficiency of 11 b/s/Hz. A total of 370 dense wavelength-division multiplexed (DWDM) channels spanning the optical C- and L-bands spaced at 25 GHz were used. Each 25-GHz channel were subdivided into four subbands, with each subband carrying a 73.5-Gb/s orthogonal frequency-division multiplexed (OFDM) signal modulated with polarization-division-multiplexing (PDM) 128-ary quadrature amplitude modulation (QAM) at each modulated subcarrier. This experiment was enabled by digital signal processing (DSP) pre-equalization of transmitter impairments, all Raman amplification, heterodyne coherent detection, and DSP postequalization of the channel and receiver impairments, including pilot-based phase noise compensation.

We report the first superchannel field experiment where two multicarrier signals at 450 Gb/s and 1.15 Tb/s are copropagated with 112-Gb/s neighbors over 45 × 79.1 km spans of field-installed fiber with erbium-doped fiber amplifiers after each span. The superchannels use zero-guard interval all-optical orthogonal frequency-division multiplexing, with each optically generated subcarrier modulated by dual-polarization quadriphase-shift-keying signals (DP-QPSK). The heterogeneous data-rate channels are aggregated using wavelength selective switch in a flexible grid wavelength-division multiplexing architecture. The net spectral efficiencies of the channels vary from 2 b/s/Hz for the 112-Gb/s channels, to 3.33 b/s/Hz for the 1.15-Tb/s superchannel. We demonstrate that any of the signals can be detected using a common filterless digital coherent receiver. In particular, tuning a local oscillator laser midway between two optically generated subcarriers enables the coherent receiver (with proper signal-processing algorithm) to demodulate two subcarriers in one data capture. This allows flexible downconversion across the whole signal band. Our results show that superchannels can coexist harmoniously with 100 G DP-QPSK signals. Even though the superchannels use the same modulation format per subcarrier as the 100 G signals, the absence of guard bands enables higher spectral efficiency that is achievable with single-carrier modulation with minimal sacrifice in reach.

Next-generation optical access networks are envisioned to evolve into a converged, high-speed, multiservice platform supporting residential, business, mobile backhaul, and special purpose applications. Moreover, bandwidth demand projections suggest that terabit aggregate capacity may need to be reached in such next-generation passive optical networks (PON). To satisfy these requirements while leveraging the large investments made in existing fiber plants, a wavelength division multiplexed (WDM)-based long-reach PON architecture combined with a multiple access technology that features a passive last-mile split, large per-λ speeds, and statistical bandwidth multiplexing can be exploited. In this paper, the first terabit PON based on hybrid WDM orthogonal frequency division multiple access (OFDMA) technology is proposed and experimentally verified. To enable high-speed, long-reach transmission with simplified optical network unit (ONU)-side digital signal processing, multiband OFDMA with ONU-side sub-band selectivity is proposed. Design challenges and tradeoffs between analog and digital domain sub-band combining and selection are also discussed. Finally, the experimental setup and results of the first 1.2 Tb/s (1 Tb/s after overhead) symmetric WDM-OFDMA-PON over 90 km straight single-mode fiber and 1:32 passive split, featuring multiband OFDMA, digitally selective ONUs, and a coherent-receiver OLT are presented and analyzed. By supporting up to 800 ONUs with 1.25/10 Gb/s guaranteed/peak rates and exhibiting a record rate-distance product achieved in long-reach PON, the demonstrated architecture may be viewed as promising for future converged terabit optical metro/access.

A 1.5 Tb/s super-channel is generated using all-optical orthogonal frequency-division multiplexing (OFDM) and dual-polarization 16QAM modulation without guard interval. We investigated the effects of DSP oversampling and receiver bandwidth using experimental results and numerical simulations to evaluate our receiver design. The super-channel is transmitted over 1200 km of standard single-mode fiber on existing 100 GbE network using only 200 GHz of optical bandwidth and detected using digital coherent receiver, achieving a spectral efficiency of 7 bit/s/Hz the highest reported to date for all-optical OFDM techniques.

We report the successful transmission of 64 Tb/s capacity (640 ×107 Gb/s with 12.5 GHz channel spacing) over 320 km reach utilizing 8-THz of spectrum in the C+L -bands at a net spectral efficiency of 8 bit/s/Hz. Such a result is accomplished by the use of raised-cosine pulse-shaped PDM-36QAM modulation, intradyne detection, both pre- and post-transmission digital equalization, and ultra-large-area fiber. We discuss in detail the digital modulation technology and signal processing algorithms used in the experiment, including a new two-stage, blind frequency-search-based frequency-offset estimation algorithm and a more computationally efficient carrier-phase recovery algorithm.

The broadband penetration and continuing growth of Internet traffic among residential and business customers are driving the migration of today's end user's network access from cable to optical fiber and superbroadband wireless systems The integration of optical and wireless systems operating at much higher carrier frequencies in the millimeter-wave (mm-wave) range is considered to be one of the most promising solutions for increasing the existing capacity and mobility, as well as decreasing the costs in next-generation optical access networks. In this paper, several key enabling technologies for very high throughput wireless-over-fiber networks are reviewed, including photonic mm-wave generation based on external modulation or nonlinear effects, spectrum-efficient multicarrier orthogonal frequency-division multiplexing and single-carrier multilevel signal modulation. We also demonstrated some applications in wireless-over-fiber trials using these enabling techniques. The results show that the integrated systems are practical solutions to offer very high throughput wireless to end users in optically enabled wireless access networks.

We have proposed and experimentally demonstrated a novel scheme to realize polarization-insensitive all-optical upconversion for single-channel or wavelength-division multiplexing signals. This scheme is based on the copolarized-pump four-wave mixing effect in nonlinear media. The copolarized pump is generated by using optical carrier suppression in an external intensity modulator; therefore, the two pumps are always parallel and phase locked. This scheme has some unique advantages for the integration between optical transport networks and radio-over-fiber systems, such as a polarization-insensitive, low-frequency bandwidth requirement for optical and electrical components, and high wavelength stability.

We investigate 40-Gb/s cost-efficient transmitter for access and metro networks. This 40-Gb/s transmitter comprises a standard directly modulated distributed-feedback (DFB) laser and a subsequent optical filter. Large dispersion tolerance of this transmitter is realized by chirp control through the phase correlation between adjacent bits for the destructive interference in order to erase the power of ldquo0rdquo bits while enhancing the extinction ratio. The chirp model of the DFB laser and the optimum parameters of the optical filter have been numerically analyzed. The chirp-managed 42.8-Gb/s transmission over 20-km standard single mode fiber (SSMF or SMF-28) without dispersion compensation and a centralized lightwave WDM-PON system are experimentally demonstrated. We have also realized the transmission over 100-m graded index plastic optical fiber (GI-POF). Moreover, the application in the metro network over 240-km SSMF or SMF-28 has also been investigated in this paper.

We have designed and experimentally demonstrated radio-over-fiber (ROF) systems to simultaneously generate optical millimeter-wave (mm-wave) and centralized lightwaves using one low-bandwidth intensity modulator (IM) with low-frequency local oscillator (LO) signals while simplifying the transmission design and reducing the cost of the base station (BS). The techniques based on double-sideband (DSB) and single-sideband (SSB) signals for ROF systems are discussed in detail in terms of architecture efficiency, bandwidth requirement, and fiber transmission performance. The repetitive frequency of the optical mm-wave carriers are four times of that of the LO in central office (CO) by using DSB scheme. Full-duplex transmission services have been successfully realized over 20-km single-mode fiber (SMF) based on wavelength-reuse technique. In order to mitigate chromatic dispersion, the SSB technique has also been investigated in this paper. We had realized an ROF system that attained dispersion-free transmission and a negative power penalty by using SSB generation. We also quantified the optical carrier-to-sideband ratio (CSR) of downstream transmission in this ROF link and established that the performance of ROF system can be significantly improved when the optical signals are transmitted at a CSR value of 0 dB. The proposed architectures require much less bandwidth of the modulators, receiver sensitivity, system operation efficiency, and reliability.

We propose a novel dispersion-free interleaver using optical delay lines by accurately locating the zeros in the transfer function. It has been implemented with the design of interleaver pairs with the same amplitude responses but opposite phase responses for bidirectional dense wavelength-division multiplexed (DWDM) transmission systems. The measured results are consistent with device simulation. We have further modified the original three-port design using unidirectional amplification, and a fourport interleaver has been built and demonstrated to achieve bidirectional DWDM transmission. In this paper, we fully studied and verified the applications of our four-port interleavers in bidirectional transmission. We demonstrated a bidirectional strain-line system over 210 km and a recirculating loop transmission over a 500-km standard single-mode fiber using 10-Gb/s on-off keying signals. Furthermore, we also demonstrated return-to-zero differential phase-shift keying (DPSK) and nonreturn-to-zero DPSK modulation formats for more than 230 km of transmission. For comparison, the different amplification functions, such as the erbium-doped fiber amplifier and the semiconductor optical amplifier, have also been probed in this paper. The experimental results have clearly illustrated the desirable functions of this novel bidirectional amplifier in this dispersion-free interleaver.

We propose an optical gas sensing network directly overlaid onto optical access networks, hybrid TDM/WDM-PONs. Centralized remote gas monitoring is demonstrated using three different sensing technologies: Chirp Laser Dispersion Spectroscopy (CLaDS), Direct Laser Absorption Spectroscopy (DLAS) and tunable diode laser absorption spectroscopy (TDLS). DLAS performs fast threshold detection while CLaDS provides quantitative information about the gas. Additionally, TDLS utilizes a cost-effective solution for multiple gases detection. The results confirm that centralized remote gas sensing can be realized in optical communication networks using standard single-mode fiber (SMF), which provides a real time, low cost, and maintenance-free solution.

A periodic add/drop system in a fiber ring network was investigated using a reconfigurable optical add/drop multiplexer (ROADM) in a re-circulating fiber loop. After seven cascaded add/drop nodes at every 150 km along the transmission, at bit error ratio (BER) equals to 10 −9 and data rate of 10 Gbps, we observed a 2.5 dB power penalty for the passing through channels with 1050 km transmission distance, and 0.3 dB sensitivity penalty variation for the periodic add/drop channels at every 150 km, respectively.

A multiwavelength fiber ring laser that is based on an S-band erbium-doped fiber amplifier (EDFA) and a semiconductor optical amplifier (SOA) is developed. An optical switch is used to switch the multiwavelength fiber laser between S-band and L-band. This fiber laser can stably lase seven wavelengths in the S-band or 28 wavelengths in the L-band. Additionally, the lasing wavelengths with a signal-to-noise ratio of over 33 dB and a wavelength spacing of 100 GHz are demonstrated experimentally. The average powers of the lasing wavelength in the S-band and the L-band are −7.53 and −12.15 dBm, respectively.