Realization optical signal processing components using SOA

This paper simulated simultaneously AND and NOT logic gate with frequency converter by using semiconductor optical amplifier. These logic gates and frequency converter are obtained with SOA effects like XGM and FWM of signals. Simulative realization of these logic gates and frequency converter will lead revolution in optical signal processing for high speed operation.     

Simple optical preprocessing for optical clock recovery using a single fiber Bragg grating filter

We propose a simple optical preprocessing for optical clock recovery using a fiber Bragg grating (FBG) filter. In the proposed scheme, the signal preprocessing is performed by suppressing the carrier component through the FBG filter, and experiment shows that the clock component is larger than about 10 dB compared with other rf components within a distance of from the clock frequency component.     

All optical clock division and multiplication by injection mode-locked laser based on SOA

Optical clock division and multiplication were realized with an injection mode-locked fiber ring laser based on semiconductor optical amplifier SOA owing to the relatively long recovery time of carriers in SOA and the rational harmonic mode-locking. Second frequency division and 1.5th frequency multiplication of 10 GHz, second and th frequency division of 20 GHz optical pulse trains were realized, respectively, in the experiment.     

A subcarrier demultiplexing scheme based on a coefficient-switchable microwave photonic filter in radio-over-fiber systems

A flexible method for subcarrier demultiplexing in radio-over-fiber (RoF) systems is proposed and experimentally demonstrated. The subcarrier demultiplexer is realized by a coefficient-switchable microwave photonic filter, which is based on biasing Mach–Zehnder modulator (MZM) at different transmission slopes. The 2.4 GHz and 2.7 GHz subcarrier signals both modulated with 100 Mbps on-off keying (OOK) data are transmitted and demultiplexed in the RoF system. The experimental result shows that each of the two subcarriers can be individually selected out with the other one well depressed. The proposed subcarrier demultiplexing scheme is simple, feasible, cost-effective and has good potential applications in the multiplexed RoF systems.     

Simultaneous demultiplexing, data regeneration, and clock recovery with a single semiconductor optical amplifier based nonlinear-optical loop mirror

We demonstrate simultaneous demultiplexing, data regeneration and clock recovery at 10Gbits/s, using a single semiconductor optical amplifier-based nonlinear-optical loop mirror in a phase-locked loop configuration.     

Synthesis of multifunction optical filter based on digital signal processing method

By a digital signal processing method, a multifunction optical filter is synthesized. The filter is formed by a Mach–Zehnder interferometer with two cascaded double-ring resonators and a single-ring resonator on the two arms respectively. It can operate as a symmetrical interleaver, an asymmetrical interleaver with arbitrary duty cycles, a notch filter with a single notch point and a notch filter with two notch points. These four functions can be realized by choosing appropriate structural parameters. The configurable and tunable features make it useful in the future intelligent optical communication networks.     

Single SOA based all-optical adder assisted by optical bandpass filter: Theoretical analysis and performance optimization

A simple and compact configuration of all-optical adders implemented with a single semiconductor optical amplifier (SOA) and optical bandpass filter (OBF) is presented in this paper. A comprehensive SOA model is put forward to investigate the output characteristics of the all-optical adders. The numerical simulation results demonstrate the influence of these key parameters, including input pulse peak power, pulsewidth, repetition rate, and OBF characteristics. Moreover some design rules are extracted for the proper selection of these parameters so as to ensure optimum performance. The obtained results confirm the feasibility of our configuration.     

S, C, L-band signal transmission using a widely tunable optical clock generator

A widely tunable optical clock pulse train generation and transmission experiments with the generated pulse train are demonstrated. The clock pulse train is generated by means of all-optical wavelength conversion using seed clock signal, probe signal, and single semiconductor optical amplifier (SOA) with the gain peak wavelength at short side. By adjusting the injected signal powers into the converter, the generated clock pulse train at the bit-rate of 10 Gb/s has high optical signal-to-noise ratio (OSNR) and low excess timing-jitter in a wide operating wavelength range. We also demonstrate 20-km transmission experiment using the generated signal in the range of 1460–1610 nm. In this experiment, we achieve transmission performances comparable to that of 1550 nm seed clock signal.     

A Kalman filter based synchronization scheme for telescope array receivers in deep-space optical communication links

In this paper, the impact of random synchronization errors on the performance of ground-based telescope array receivers for an inter-planetary optical deep-space communication (ODSC) link is investigated. An adaptive method based on Kalman filters is developed for the synchronization and combination of different telescope signals in the array. An end-to-end simulation platform for ODSC link between Earth and planet Mars is implemented that incorporates pulse-position modulation (PPM), direct-detection array receivers, and photon-counting detectors. The effects of atmospheric turbulence and background noise are also modeled. The performance of array receivers is evaluated in terms of probability of symbol error and achievable data rates. The simulation results show that the Kalman filter-based synchronization scheme keeps the synchronization induced power losses to less than 1 dB. The analysis also shows that in the worst-case operational scenario and presence of random synchronization errors, an array consisting of hundred, 1 m telescopes performs almost similar to a single 10 m telescope. Hence, the degradation in the combined signal due to synchronization errors places a minor limitation on the number of telescopes in a telescope array receiver consisting of up to 100 telescope elements.     

A novel successive demultiplexing scheme based on optical-CDMA balanced demodulation for FBG sensor systems

In order to increase the multiplexing density of the fiber Bragg gratings （FBGs） for a low cost per-sensor, based on the analysis of the spectrum shadow distortion （SSD）, a novel successive demultiplexing scheme for FBG sensors has been developed. It is based on the optical cade division multiple access （CDMA） balanced demodulation. A high-density multiplexing-demultiplexing system for FBG sensors has been designed, and corresponding simulation carried out has demonstrated that the FBG sensors＇ reflective signals can still be obtained accurately and respectively, even if FBG sensors＇ operating bandwidths heavily overlap. The SSD has been greatly mitigated.     

Tunable optical filter based on Sagnac phase-shift using single optical ring resonator

In this paper, a single optical ring resonator connected to a Sagnac loop is used to demonstrate theoretically a novel narrow band optical filter response that is based on Sagnac phase-shift Δφ. The given filter structure permits the Sagnac rotation to control the filter response. It is shown that by changing the Sagnac rotation rate, we can tune the filter response for desired bandwidths. To increase the wavelength selectivity of the filter, the Sagnac phase-shift should be as small as possible that is limited by the loop length. For Δφ=0.1 rad, the obtained FWHM is 2.63 MHz for tuning loop length of 2 m. The simulation response agrees fairly with the recently reported experimental result.     

Simultaneous demultiplexing and clock recovery using a single electroabsorption modulator in a novel bi-directional configuration

A single electroabsorption modulator was used to demultiplex a 10 Gbit/s channel from a 40 Gbit/s OTDM data stream, whilst simultaneously recovering the 10 GHz electrical clock. This was achieved using a new bi-directional operation of the EA modulator, combined with a simple phase-locked loop feedback circuit. Excellent system performance was achieved, indicating that operation up to and beyond 100 Gbit/s is possible using current technology.     

用双稳开关实现光学时分复用的方法

提出一种用全光学开关构成时分复用系统的方法,并用ZnS干涉滤光片双稳开关进行了实验演示.如果采用高速开关进行替代,可望用于光通信与光计算系统,提高信息的传输速度.     

Femtosecond fiber laser based methane optical clock

An optical clock based on an Er³⁺ fiber femtosecond laser and a two-mode He–Ne/CH₄ optical frequency standard (λ=3.39 μm) is realized. Difference-frequency generation is used to down convert the 1.5-μm frequency comb of the Er³⁺ femtosecond laser to the 3.4-μm range. The generated infrared comb overlaps with the He–Ne/CH₄ laser wavelength and does not depend on the carrier–envelope offset frequency of the 1.5-μm comb. In this way a direct phase-coherent connection between the optical frequency of the He–Ne/CH₄ standard and the radio frequency pulse repetition rate of the fiber laser is established. The stability of the optical clock is measured against a commercial hydrogen maser. The measured relative instability is 1×10⁻¹² at 1 s and for averaging times less than 50 s it is determined by the microwave standard, while for longer times a drift of the He–Ne/CH₄ optical standard is dominant.     

Flexible polarization demultiplexing method based on an adaptive process noise covariance Kalman filter

A flexible polarization demultiplexing method based on an adaptive Kalman filter(AKF) is proposed in which the process noise covariance has been estimated adaptively. The proposed method may significantly improve the adaptive capability of an extended Kalman filter(EKF) by adaptively estimating the unknown process noise covariance. Compared to the conventional EKF, the proposed method can avoid the tedious and time consuming parameter-by-parameter tuning operations. The effectiveness of this method is confirmed experimentally in 128 Gb/s 16 QAM polarization-division-multiplexing(PDM) coherent optical transmission systems. The results illustrate that our proposed AKF has a better tracking accuracy and a faster convergence(about 4 times quicker)compared to a conventional algorithm with optimal process noise covariance.     

Ultra high-speed optical signal processing based on single SOA at 60 Gb/s

The paper shows the design of all-optical logic gates OR, AND, NOT, NOR, XNOR, XOR at ultra high speed by using SOA. The simulations of all logic gates are obtained by XGM and FWM in SOA at 40 Gb/s and 60 Gb/s. The OR, AND, NOR logic between two data sources are obtained using a pump signal, while another logic XNOR using two data. The NOT, XOR obtained using FWM and XGM combined. Thus realization of these logics at 40 Gb/s and 60 Gb/s will lead revolution growth in optical signal processing for high-speed operation.     

Simultaneous clock recovery and demultiplexing of a 320 Gb/s OTDM system using an optoelectronic oscillator based on cascaded MZM and PolM

An improved optoelectronic oscillator scheme for an optical time division multiplexing(OTDM) system based on cascaded Mach-Zehnder modulator(MZM) and polarization modulator(PolM) is experimentally investigated.The system can simultaneously realize clock recovery and demultiplexing.With the MZM working at peak point to generate return-to-zero-33 optical pulses and the PolM working as an equivalent intensity modulator,a high-quality clock signal with 35-fs timing jitter is extracted from the 160-GBaud OTDM-differential quaternary phase-shift keying signal.Narrow short optical switch gates(4 ps) are also generated to demultiplex 160-GBaud signals to 40-GBaud signals.Error-free performance is achieved with 2.4-dB power penalty in the worst case.     

Influence of filter and signal types in optical matched filtering

The dependence of the output correlation signal on the filter parameters, filter types, and signal types in matched filtering is discussed. On the basis of the established filter criteria—the signal-to-noise ratio, peak-to-sidelobe ratio, and diffraction efficiency—a new measure is introduced giving an overall estimate of the feasibility of filters. According to that single measure, various filter types are compared and selected by numerical experiments.     

Diffractive optical elements for implementing spatial demultiplexing and spectral synthesizing simultaneously

Diffractive optical elements (DOEs) are designed for implementing spatial demultiplexing and spectral synthesizing simultaneously by using conjugate gradient optimization algorithm. Three different design cases for the spectrum window of the optical communication: three discrete spectral segments in one direction, two discrete spectral segments in two directions, and three discrete spectral segments in three directions, are implemented. The numerical simulations indicate that the designed multi-functional DOEs can successfully generate desired spectra at predesigned directions. These designs can provide a useful information for designing the wavelength division multiplexer and the arrayed waveguide grating in various optical systems.     

Frequency selective surfaces for millimetre and submillimetre wave quasi optical demultiplexing

The purpose of this paper is to compare the filtering properties of drilled plate and printed element frequency selective surfaces in the range 80 – 800 GHz. Novel techniques for measuring and fabricating the devices are described, and close agreement is shown between numerical simulation and experimental results.