Light slowing and all-optical time division multiplexing of hybrid four-wave mixing signal in nitrogen-vacancy center

We report the experimental results of hybrid four-wave mixing and fluorescence signals from nitrogen-vacancy(NV)centers in diamond. The fluorescence signals are slowed owing to dark state. The observed delay time of light slowing due to interconversion between NV^- and NV^0 is about 6.4 μs. The relative intensities of read-out signals change with the wavelength and power of writing pulse. Based on light slowing, we present the model of all-optical time division multiplexing. The intensity ratio in different demultiplexed channels is modulated by the wavelength and power of control field. It has potential applications in quantum communication and all-optical network.

Novel Optical Analog-To-Digital Converter Based on Optical Time Division Multiplexing

A novel optical analog-to-digital converter based on optical time division multiplexing(OTDM) is described which uses electrooptic sampling and time-demultiplexing together with multiple electronic analog-to-digital converter(ADC). Compared with the previous scheme, the time-division multiplexer and the time-division demultiplexer are applied in the optical analog-to-digital converter(OADC) at the same time, the design of the OADC is simplified and the performance of the OADC based on time-division demultiplexer is improved. A core optical part of the system is demonstrated with a sample rate of 10 Gs/s. The signals in three channels are demultiplexed from the optical pulses.The result proves our scheme is feasible.

Designing of an all-optical time division multiplexing scheme with the help of nonlinear material based tree-net architecture

In the field of optical interconnecting network and in super fast photonic computing system, the tree architecture and optical nonlinear materials can play a significant role. Nonlinear optical material may find important uses in optical switching. Optical switch using nonlinear material makes it possible for one optical signal to control and switch another optical signal through nonlinear interaction in a material. In this communication such materials have been successfully exploited to design an all-optical tree-net architecture, which can be utilized for time division multiplexing scheme in all-optical domain.

Full color ghost imaging by using both time and code division multiplexing technologies

We propose a new full color ghost imaging scheme using both time and code division multiplexing technologies.In the scheme,the speckle patterns of three colors(red,green and blue)are modulated with different time slots and codes.The light intensity is sampled by one bucket detector.Then based on the modulated time slots and codes,we can effectively and simultaneously extract three detection component signals corresponding to three color components of objects from the sampling signal of the bucket detector.Finally,three component images resulting from the three component detection signals can be synthesized into a full color image.The experimental results verify the feasibility of our scheme under the limit of the number of time slots and codes.Moreover,our scheme reduces the number of bucket detectors and can realize high quality imaging even in a noisy environment.

Effects of residual second- to fourth-order dispersion in ultra high-speed optical time division multiplexing transmission

We present an expression of maximum fiber-link length, at which the output pulses can return to its original rms time width, in an optical fiber link with up to fourth-order dispersion. The fourth order dispersion is compensated by combination of the effects of proper source chirping and negative residual second-order dispersion. The interesting fact is that the optical pulses can restore itself at a longest distance even in case of chirp parameter being positive, as well as being negative traditionally. The validity of the analytical formulas is also confirmed by split-step Fourier numerical stimulation.

Design of Simulation for Time-Division Multiplexing Digital Optimal Frequency Band Transmission System

This paper designs a simulation experiment model of the overall structure of time-division multiplexing digital optimal frequency band transmission system based on MATLAB simulation platform. The parameters of each module in the simulation model are set. The working process and performance of the time-division multiplexing digital optimal band transmission system are simulated. The simulation results show that the digital optimal band transmission system achieves the best transmission receiving conditions and performance, and the designed time-division multiplexing optimal digital band transmission simulation system achieves its functions. The research in this paper will help to improve the level of digital communication technology and to understand the structure of time-division multiplexing digital optimal band transmission system.

Combination of light-emitting diode positioning identification and time-division multiplexing scheme for indoor location-based service

A combination of light-emitting diode（LED） identification and a time-division multiplexing scheme is proposed in this Letter for indoor location-based service. With the scheme, the arrangement of white LED lamps and the structure of a data frame are designed to realize high-accuracy indoor positioning and location-based payload data transmission simultaneously. The results of the experiment demonstrate that the indoor positioning accuracy is 10 cm and 2 Mb/s data transmission with high signal quality is realized.

Time-division multiplexing holographic display using angular-spectrum layer-oriented method(Invited Paper)

A time-division multiplexing method for computer-generated holograms （CGHs） is proposed to solve the problem of the limited space-bandwidth product. A three-dimensional （3-D） scene is divided into multiple layers at different depths. The CGH corresponding to each layer is calculated by an angular-spectrum algorithm that is effective at a wide range of propagation distances. All of the CGHs are combined into several group-CGHs. These group-CGHs are sequentially uploaded onto one spatial light modulator at a high frame rate. The spacebandwidth product can be benefited by the time-division processing of the CGHs. The proposed method provides a new approach to achieve high quality 3-D display with a fast and accurate CGH computation.

All-Optical Switches in Optical Time-Division Multiplexing Technology: Theory, Experience and Application

Optical time division multiplexing (OTDM) is one of the promisinig ways for the future high speed optical fiber communication networks. All optical switch is, being one of the core technologies of OTDM systems and networks, crucial to realize the various signal processes including time division demultiplexing, packet switching, all optical regenerating and so on. This thesis mainly studies various all optical switch technologies and their utilization in the fields of all optical signal processings in the OTDM systems and networks. The main jobs are listed as follows.\; (1) A novel all optical ultrafast demultiplexing scheme using the soliton self trapping effect in birefringent fiber is proposed.\; (2) The demultiplexing performance of the Nonlinear Optical Loop Mirror(NOLM) is thoroughly analyzed and its optimization is further discussed.\; (3) The performance analysis and the configuration optimization of the all optical switches based on the Semiconductor Optical Amplifier(SOA) are systematically presented. The speed limitation of the all optical SOA switches induced by the fast gain depletion of SOA is discussed. Besides, a novel SOA switch is proposed, which adopts the asymmetric Mach Zehnder Interferometer configuration.\; (4) The 8×2\^5 Gb/s OTDM experimental transmission system along 105 km standard fiber is realized using the NOLM demultiplexer.\; (5) The NOLM switch is used to realize the all optical 3R regeneration of 2\^5 Gb/s Return to Zero signal.\; (6) The feasibility and limitation of the all optical SOA packet switch is discussed. And a developed MZI configuration of SOA packet switch is further shown to improve the packet switching performance. Finally, an all optical packet dropping node suitable in the networks with ring or bus configuration and an all optical packet switching node in the ShuffleNet networks are proposed to show the feasibility of all optical packet switching through combining the all optical switches and the reasonable logic decisions.

Crosstalk-aware RCSA for spatial division multiplexing enabled elastic optical networks with multi-core fibers

In this Letter, we propose two crosstalk-aware routing, core, and spectrum assignment （CA-RCSA） algorithms for spatial division multiplexing enabled elastic optical networks （SDM-EONs） with multi-core fibers. First, the RCSA problem is modeled, and then a metric, i.e., CA spectrum compactness （CASC）, is designed to measure the spectrum status in SDM-EONs. Based on CASC, we propose two CA-RCSA algorithms, the first-fit （FF） CASC algorithm and the random-fit （RF） CASC algorithm. Simulation results show that our proposed algorithms can achieve better performance than the baseline algorithm in terms of blocking probability and spectrum utilization, with FF-CASC providing the best performance.

Highly-sensitive NO,NO2,and NH3 measurements with an open-multipass cell based on mid-infrared wavelength modulation spectroscopy

A compact prototype based on mid-infrared wavelength modulation spectroscopy（WMS）is developed for the simul-taneous monitoring of NO,NO2,and NH3 in the urban area.Three quantum cascade lasers（QCLs）with central frequencies around 1900.0 cm^-1,1600.0 cm^-1,and 1103.4 cm^-1are used for NO,NO2,and NH3detections,respectively,by timedivision multiplex.An open-path multi-pass cell of 60-m optical path length is applied to the instrument for high sensitivity and reducing the response time to less than 1 s.The prototype achieves a sub-ppb detection limit for all the three target gases with an average time of about 100 s.The instrument is installed in the Jiangsu environmental monitoring center to conduct performance tests on ambient air.Continuous 24-hour measurements show good agreement with the results of a reference instrument based on the chemiluminescence technique.

Demonstration of a 4-Sensor Folded Sangac Sensor Array with Active Phase Biasing Scheme

A 4-sensor folded Sagnac sensor array with an active phase biasing scheme is presented. The overlapping of the signal and noise pulse is avoided through a time division multiplexing scheme and the noise pulses is eliminated almost completely. The scheme can address 16 sensors when the repeat frequency of input pulse is at 68.3 kHz. The alternative phase bias technique is demonstrated, which can provide sensors with stable phase bias. The future benefit of this technique is that the 1/f noise in the circuit can be suppressed.

Fault monitoring in passive optical network using code division multiplex-based dual-OTDR traces comparison

A dual optical time domain reflectometry （OTDR） system, which employs two different continuous waves at the optical line terminal and a pair of fiber Bragg gratings at the end of each optical network unit, is proposed in a time-division multiplexing passive optical network （PON）. The proposed scheme accomplishes the fiber fault monitoring by comparing the different wavelength＇s testing curves. Complete complementary code is utilized to measure multiple wavelength signals simultaneously with only one receiver and to improve the dynamic range of this system. The PON system consisting of 20 km feeding fiber and a 1：16 splitter is investigated by the experiments. The experimental results show that the faulty branch can be successfully identified by using our scheme. What is more, we also demonstrate that our scheme can be applied to the multi-stage PON.

New Structure for Multi-Channel Demultiplexing

A new all optical demultiplexer based on nonlinear effect in semiconductor laser amplifier (SLA) is proposed. It can demultiplex all channels of the OTDM signal concurrently, and it can also be integrated on a single chip. The proposed device consists of a series short Fabry Perot amplifiers (FPSLA) setting on the path vertically, through which the preamplified optical signal travels. Perpendicularly to the signal, K(channel number) paralleled beams of light pulse, which act as probes with repetition at the bit rate of one channel, irradiate on these FP SLAs , respectively, just when the corresponding signal channel pulse passes through the active region from lateral side. The transmissivity depends on the signal pulse. Theoretical analysis has been given. As a demonstrating example, a device operated at the speed of 25Gbit/s (2.5Gbit/s×10 ) is simulated and the results show that the about 9.24 dB extinction ratio can be achieved easily.

Ultra-Thin Flexible Eddy Current Sensor Array for Gap Measurements

An ultra-thin flexible eddy current proximity sensor array was developed for online measurements of tiny gaps between large smooth metallic and nonmetallic surfaces of arbitrary shapes. The probe of the flexible eddy current sensor array, which includes a set of sensor coils, is fabricated on a thin flexible substrate using the flexible printed circuit board process which allows the probe to be very thin and flexible so that it can conform to the surface geometry of the measured objects. The sensor coils are connected to an inductance-capacitance oscillator, which converts the distance between the sensor coil and the metallic target to a frequency output. Experimental results show that the measurement accuracy of the sensor system can reach ±0.5% for a 2-mm gap and the sensor system is suitable for online gap measurements.

Dynamic PMD compensation in 40-Gb/s optical communication system

A 40-Gb/s optical time division multiplexing (OTDM) return-to-zero (RZ) transmission experiments including a dynamic polarization mode dispersion (PMD) compensation was reported. The dynamic PMD compensator is made up of two-stage four degrees of freedom (DOF). The first stage adopts polarization controller and fixed time-delayed line. The second stage is variable differential group delay (DGD) element. The PMD monitoring technique is based on degree of polarization (DOP) as error signal. A novel practical adaptive optimization algorithm was introduced in dynamic adaptive PMD compensation. The experimental results show that the performance of the PMD compensator is excellent for 40-Gb/s RZ transmission systems with the large DGD. With this compensator, a significant improvement of system performance can be achieved in the eye pattern of a received signal. The first-order compensating ability of the compensator is greater than 30 ps. The second-order compensating ability is greater than 200 ps2. The first-order optimum compensating time is within 10 ms. The second-order optimum compensating time is within 24 ms.

Polarization Multiplexed Interrogation Technique for FBG Sensor Array

This paper proposes a polarization multiplexed interrogation technique for fiber Bragg grating （FBG） sensor array. The novelty of the proposed model is its ability to reduce interference and cross talk, thus allowing larger number of FBG sensors to be interrogated in an array. The calibration technique has been illustrated in this work for the FBG sensor array, where data from each sensor are linearly polarized and multiplexed before co-propagation, to find out the tapping points that enable identification of each sensor data uniquely. Simulation has been carried out for odd number and even number of sensors in an array. Even with interfering input, this proposed scheme can interrogate and distinctively identify each sensor data using appropriate tuning of polarization-splitter, polarization-rotator, and polarization-attenuator at the detector end during the calibration process. The significance of the proposed method is its compact size, which makes this calibration system ready to be deployed in real-time sensing applications and data acquisition from the FBG sensor array.

Field-programmable gate array-based large-capacity sensing network with 1642 ultra-weak fiber Bragg gratings

A field-programmable gate array （FPGA）-based large-capacity sensing network with ultra-weak fiber Bragg gratings （FBGs） is proposed and experimentally studied. The demodulation system is constructed to interrogate 1642 serial time-division-multiplexing FBGs with a peak refleetivity of about -40 dB and equal separations of 2.5 m. Two semiconductor optical amplifiers and an InGaAs linear sensor array controlled by an FPGA are introduced to the demodulation system to achieve fast, precise, and flexible interrogation. The low crosstalk and spectral distortion axe investigated through both theoretical analysis and experiments.

Investigation of switching-window in a gain-transparent UNI configuration

Switching-window in an interferometric configuration of a gain-transparent ultrafast nonlinear interferometer (gt-UNI) is investigated numerically. The phase change is observed in detail. To assess the performance of switching window, the integrated contrast ratio (ICR) is introduced. For the data pulse with the bit width of 6.25 ps and with the energy of 60 pJ, respectively, the ICRs in different situations are simulated using modified nonlinear Schrodinger equation (MNLSE) considering of the carrier depletion pulsation (CDP), carrier heating (CH), and spectral-hole burning (SHB). The results show that the maximum ICR is located at the optimum position of the semiconductor optical amplifier (SOA) that is determined by the width and energy of the control pulse.