Distributed acoustic sensing technology is gaining attention as a valuable tool for seismic monitoring, oil and gas pipeline imaging, and underwater cable observation. Phase-sensitive Optical Time Domain Reflectometry (see abstract for this (phi -OTDR) is a popular technique within this field, known for its ability to recover high signal-to-noise ratio acoustic vibration signals. However, traditional see abstract for this phi-OTDR systems have limitations in observing both local microseismic events and strong seismic motions simultaneously and requiring months of data analysis and processing time. To address this, a fast recovery system based on multi-sideband pulse modulation is proposed. This system allows for simultaneous detection of different strain ranges at a low sampling rate, effectively managing large data volumes and enabling fast demodulation. This work will bring some inspiration to engineering applications and instrumentalization.
We propose and demonstrate an optical fiber probe which can simultaneously detect low and high-wavenumber coherent anti-Stokes Raman scattering (CARS) spectrum of samples. The low and high-wavenumber resonance signals are excited by the pump pulses and dual-Stokes pulses which are generated by the soliton self-frequency shift. The optical fiber taper probe focuses and delivers CARS excitation pulses to the samples. The detection of low and high-wavenumber regions can be achieved by the characterization of CN triple stretching vibrations and CH stretching vibrations. The simultaneous low and high-wavenumber optical fiber CARS probe will enable wider applications of quantitative chemical detection in in vivo biomedical research.
A dynamic strain range extension method is proposed for fiber distributed sensing system based on dual-sideband frequency modulation pulse. Aiming at the problem of huge raw data and slow processing speed of the dual-sideband system, the RF circuit module scheme and corresponding algorithms are proposed to enhance the system's ability to apply to real-world scenarios. This study extends the range of measurable dynamic strain in the system and effectively tackles the challenges of storage and computational efficiency as data volume increases. It enhances the system's ability to adapt to complex environments.
KEYWORDS: Receivers, Signal detection, Digital signal processing, Telecommunications, Photodetectors, Transmittance, Interference (communication), Space division multiplexing
The nonlinear effects in single-mode fiber and the constraints in device technology, time division multiplexing and wavelength division multiplexing cannot increase the capacity of optical fiber communication system unlimitedly. The development of space division multiplexing technology has increased the capacity of existing optical fiber communication systems by at least an order of magnitude. With the continuous improvement of transmission rate and system bandwidth in the long-haul communication, low cost and small size are also regarded as important factors in the future. In this work, the transmission performance of the low-cost self-coherent receiver and the mature coherent receiver in the long-haul mode division multiplexing system is compared. In the 32-Gbaud 6-mode dual-polarization QPSK transmission system with a fiber length of 80 km as the single span, two receiver schemes are compared considering the same configurations of the transmitter and the optical fiber link components. Compared the use of eight photodetectors integrated in the coherent receiver, the Kramers–Kronig (KK) receiver only requires two photodetectors to demodulate the dual-polarization transmission, while the phase recovery algorithm based on Hilbert transform in the KK receiver will increase the complexity of digital signal processing. Numerical results indicate that the KK receiver scheme has the advantages of lower cost and more compact size and shows the similar performance as the coherent receiver for the transmission of less than 2500 km, despite the requirement of larger transmitted power and algorithm complexity. It can also be concluded that, self-coherent receiver based on the KK algorithm can be a complementary detection solution to the coherent receiver for next-generation long-haul transmission networks with low-cost transceivers.
KEYWORDS: Telecommunications, Signal to noise ratio, Fiber optic communications, Optical amplifiers, Digital signal processing, Fiber amplifiers, Modulation, Binary data, Systems modeling
Due to the high transmission capacity, optical fiber systems have been widely applied in the modern telecommunication infrastructure to meet the ever-increasing demand of data traffic. Optical amplifiers have been employed to amplify optical signals and to compensate for the transmission losses. They play a key role in relaying the signals in ultra-wideband optical fiber communication systems. However, the amplified spontaneous emission (ASE) noise will be introduced and will pose constraints on the transmission information rates. The mutual information (MI) and the generalized mutual information (GMI) have been applied to evaluate the information rates in communication systems. In this work, we have investigated the impact of ASE noise on the MI and the GMI, and developed corresponding analyses across different modulation formats. Our work aims to explore the limit and requirements on optical amplifiers in next-generation ultra-wideband optical fiber communication systems.
Compared with traditional electrical methods, radio frequency self-interference cancellation (SIC) based on microwave photonic technology has the advantages of large bandwidth, high precision, low loss and anti-electromagnetic interference. For distributed full-duplex communication system, a SIC method based on cascade modulation is studied. The cancellation depth of the system for single-frequency signals is more than 43 dB, and the cancellation depth for wideband signals is more than 22 dB, and the recovered useful signals is obtained. The system adopts cascade modulation, and the isolation degree of LO and RF signal is high. In this scheme, the signal after SIC can be transmitted to the central office through a long fiber. The proposed approach supplies an architecture for distributed systems with both down-conversion and SIC.
KEYWORDS: Demodulation, Acoustics, Signal detection, Data acquisition, Signal processing, Optical fibers, Data processing, Spatial resolution, Optical sensing, Parallel computing
Distributed acoustic sensing technology has a wide range of applications such as seismology, mineral exploration, and so on. For practical application needs, we contributed to increase demodulation rate of optical fiber distribution acoustic sensing system. Aiming at the problem of large volume of signal acquisition data and long demodulation time, we proposed to apply a hardware circuit as a part of data acquisition system. We also applied a GPU-based fast processing algorithm to realize simultaneous calculation of different units. Through the combination of hardware and software, the fast signal demodulation based on low sampling rate was successfully realized.
Micro-cavity sustaining whispering gallery mode (WGM) has been widely used in physical parameter sensing and biosensing applications. We explored three type micro-cavity enhancement methods to realize highly sensitive optical fiber sensors. Firstly, optofluidic-enhanced micro-cavity optical fiber sensors are discussed. Secondly, optomechanical oscillation micro-cavity optical fiber sensor is introduced using a hollow silica microbubble cavity. Finally, fiber laser enhancement mechanism is proposed to avoid the difficulty in direct fabrication of active micro-cavity.
This paper proposes a fiber optic surface plasmon resonance (SPR) sensor based on the heterostructure of MoS2/WS2. Transition metal dichalcogenides (TMDCs) have been widely studied due to their high carrier mobility, excellent photoelectric properties and good biocompatibility. A heterostructure is constructed by two types of TMDCs (MoS2/WS2) and is used to improve the performance of the Ag layer coated fiber optic SPR sensor. The heterostructure film increases the integral of the electric field intensity on the surface of the sensor, thus improving the sensitivity of the sensor. The finite element analysis shows that the sensitivity of the sensor is as high as 3127.18 nm/RIU and the figure of merit is up to 70.04 RIU-1. The proposed sensor exhibits promising potential in the field of biochemical detection.
KEYWORDS: Signal to noise ratio, Telecommunications, Modulation, Optical fibers, Digital signal processing, Systems modeling, Interference (communication), Transmittance, Optical amplifiers, Optical communications
Coherent optical fiber systems can achieve long-distance, large-capacity and high data-rate transmissions. The system performance of communication systems is generally evaluated with regard to the data capacity and the transmission reach. In this work, the performance of multi-channel (up to C-band) Nyquist-spaced coherent optical communication systems has been assessed in terms of achievable information rates, transmission distances and signal-to-noise ratios, considering different influencing factors, such as nonlinearity compensation, signal input power and modulation format. Numerical simulations and enhanced Gaussian noise (EGN) model have been carried out for different modulation formats including quadrature phase shift keying (QPSK), 16-ary quadrature amplitude modulation (16-QAM), 64-QAM and 256-QAM. It is found that in C-band (151-channel) Nyquist-spaced systems, the achievable information rates at the transmission distance of 6000 km are 19.3 Tbit/s for dual-polarization QPSK (DP-QPSK), 30.9 Tbit/s for DP-16QAM, 32.0 Tbit/s for DP64QAM and 32.2 Tbit/s for DP-256QAM, respectively, when electronic dispersion compensation is applied only. Such achievable information rates can be increased up to 38.3 Tbit/s for DP-16QAM, 47.2 Tbit/s for DP-64QAM and 47.8 Tbit/s for DP-256QAM, respectively, when the nonlinearity compensation is employed.
KEYWORDS: Signal to noise ratio, Telecommunications, Digital signal processing, Optical fibers, Distortion, Optical communications, Optical amplifiers, Transmittance, Modulation, Fiber lasers
In digital signal processing (DSP) based coherent optical communication systems, the effect of equalization enhanced phase noise (EEPN) will seriously degrade the transmission performance of high-capacity optical transmission system. In this paper, we have investigated the influence of EEPN on 9-channel 32-Gbaud dual-polarization 64-ary quadrature amplitude modulation (DP-64QAM) Nyquist-spaced superchannel optical field trial by using electronic dispersion compensation (EDC) and multi-channel digital backpropagation (MC-DBP). The deteriorations caused by EEPN on the signal-to-noise-ratio (SNR) and achievable information rates (AIRs) in high-speed optical communication systems have been studied. The system performance versus back-propagated bandwidth under different laser linewidth have also been demonstrated. The SNR penalty due to the distortion of EEPN achieves ~5.11 dB when FF-DBP is implemented, which informs that FF-DBP is more susceptible to EEPN, especially when the LO laser linewidth is larger. The system AIR versus different transmission distance under different EEPN interference using EDC-only and MC-DBP have also been evaluated, which show that there is a trade-off on the selection of lasers and back-propagated bandwidths to achieve a target AIR.
The efficient and accurate evaluation of the transmission performance of high-capacity optical communication systems has always attracted significant research attentions. The enhanced Gaussian noise (EGN) model is considered as an excellent solution to predict the system performance taking into account linear and nonlinear transmission impairments. Since the conventional form of the EGN model is complicated and intractable for a fast computation, the closed-form simplification has been regarded as a direction to significantly reduce the computational complexity. However, the accuracy of such a closed-form EGN model becomes a main concern in the application of ultra-wideband optical communication systems. In this work, we have investigated the accuracy of the closed-form EGN model for ultra-wideband optical fiber communication systems, where the performance of the system using electronic dispersion compensation, multi-channel nonlinearity compensation and full-field nonlinearity compensation has been evaluated in terms of symbol rate, number of channels and signal power. Our work will provide an insight on the application of the EGN model in next-generation ultra-wideband long-haul optical fiber communication networks.
KEYWORDS: Phase shift keying, Telecommunications, Modulation, Digital signal processing, Optical communications, Signal to noise ratio, Algorithm development, Fiber optic communications, Signal detection, Interference (communication)
Nowadays, the coherent optical communication system plays an important role in communication field because of large capability and bandwidth. A coherent optical communication, based on high-order modulation and digital signal processing technologies, consists of optical transmitters, optical fiber lines, optical amplifiers and optical receivers. In the high-speed coherent optical communication system, the phase noise from the transmitter laser and the local oscillator laser can significantly degrade the performance of the signal transmission and detection, especially for the systems using high-order modulation format, such as m-ary phase shift keying (mPSK) and m-ary quadrature amplitude modulation (m-QAM). Therefore, investigations on laser phase noise compensation algorithm based on digital signal processing technologies has become more and more significant. In this work, a multi-ring carrier phase recovery algorithm is developed for compensating the laser phase noise in optical fiber communication systems using high-order modulation formats. Degradations on the performance of communication systems due to the laser phase noise have been investigated. The system performance using the proposed algorithm and the conventional Viterbi-Viterbi algorithm were also evaluated in 9-channel and 15- channel, 32-Gbaud, Nyquist-spaced QPSK, 16-QAM, 64-QAM and 256-QAM coherent transmission systems with considering the impact of the laser phase noise. It is found that the phase noise leads to stricter constraints on the linewidths of transmitter-side and receiver-side lasers, and it can greatly degrade the achievable information rates in communication systems. Besides, compared to the conventional Viterbi-Viterbi algorithm, which is usually applied in the QPSK system, our proposed algorithm can also well mitigate the laser phase noise in 16-QAM, 64-QAM and 256-QAM optical communication systems.
The effect of equalization enhanced phase noise (EEPN) will be introduced in digital signal processing (DSP) based coherent optical communication systems. The EEPN will seriously degrade the transmission performance of a highcapacity optical transmission system. In this work, the influence of EEPN on the performance of dual-polarization 16-ary quadrature amplitude modulation (DP-16QAM) optical transmission system using the electrical dispersion compensation (EDC), the single-channel digital back-propagation (DBP), the partial-bandwidth DBP and the full-field DBP (FF-DBP) were comparatively evaluated with and without considering distortions from the EEPN. Deteriorations on achievable information rates (AIRs) and modulation error ratios (MERs) of optical communication systems due to EEPN have also been assessed. Numerical results indicate that the transmission performance of coherent optical systems can be significantly degraded by the EEPN, especially when FF-DBP is used for the nonlinearity compensation. The larger the linewidth of the local oscillator (LO) laser is, the more serious the degradation caused by EEPN is. This deterioration leads to a decrease in optimal launch powers, AIRs and MERs in the long-haul optical communication systems. In the DP-16QAM transmission system, because of the interference of the EEPN generated by the LO laser with a linewidth of 1 MHz, the degradations on the AIR and MER are 0.15 Tbit/s and 4.15 dB in the case of FF-DBP, respectively. It can also be concluded that, for coherent optical systems with long transmission distances and high symbol rates, the compensation bandwidth and the computational complexity of MC-DBP in the DSP module can be significantly reduced by using narrower-linewidth LO lasers
Electrostatics plays a critical function in most biomolecules, therefore monitoring subtle biomolecular bindings and dynamics via the electrostatic changes of biomolecules at biointerfaces has been an attractive topic recently and has provided the basis in diagnosis and biomedical science. Here we present a bioelectrostatic responsive microlaser based on liquid crystal (LC) droplet and explored its application for ultrasensitive detection of negatively charged biomolecules. Whispering gallery mode (WGM) lasing from positively charged LC microdroplets was applied as the optical resonator, where the lasing wavelength shift was employed as a sensing parameter. With the dual impacts from whispering-gallery mode and liquid crystal, molecular binding signals will be amplified in such LC droplet sensors. It is found that molecular electrostatic changes at the biointerface of droplet triggered wavelength shift in lasing spectra. The total wavelength shift increased proportionally with the adhering target concentrations. Compared to a conventional polarized optical microscope, significant improvements in sensitivity and dynamic range by four orders of magnitude were achieved. Our work indicated that the surface-to-volume ratio plays a critical role in the detection sensitivity in WGM laser-based microsensors. Finally, bovine serum albumin and specific biosensing using streptavidin and biotin were exploited to demonstrate the potential applications of microlasers with a detection limit on the order of 1 pM. We anticipate this approach will open new possibilities for the ultrasensitive label-free detection of charged biomolecules and molecular interactions by providing a lower detection limit than conventional methods.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.