Optical Output Signal Research Articles

Optical fiber-based system for continuous measurement of in-bore projectile velocity

This paper reports the design of an optical fiber-based velocity measurement system and its application in measuring the in-bore projectile velocity. The measurement principle of the implemented system is based on Doppler effect and heterodyne detection technique. The analysis of the velocity measurement principle deduces the relationship between the projectile velocity and the instantaneous frequency (IF) of the optical fiber-based system output signal. To extract the IF of the fast-changing signal carrying the velocity information, an IF extraction algorithm based on the continuous wavelet transforms is detailed. Besides, the performance of the algorithm is analyzed by performing corresponding simulation. At last, an in-bore projectile velocity measurement experiment with a sniper rifle having a 720 m/s muzzle velocity is performed to verify the feasibility of the optical fiber-based velocity measurement system. Experiment results show that the measured muzzle velocity is 718.61 m/s, and the relative uncertainty of the measured muzzle velocity is approximately 0.021%.

Tuning the external optical feedback-sensitivity of a passively mode-locked quantum dot laser

The external optical feedback-sensitivity of a two-section, passively mode-locked quantum dot laser operating at elevated temperature is experimentally investigated as a function of absorber bias voltage. Results show that the reverse-bias voltage on the absorber has a direct impact on the damping rate of the free-running relaxation oscillations of the optical signal output, thereby enabling interactive external control over the feedback-response of the device, even under the nearly resonant cavity configuration. The combination of high temperature operation and tunable feedback-sensitivity is highly promising from a technological standpoint, in particular, for applications requiring monolithic integration of multi-component architectures on a single chip in order to accomplish, for instance, the dual-objectives of stable pulse quality and isolation from parasitic reflections.

Stable and wavelength-tunable RSOA- and SOA-based fiber ring laser

In this work, we propose and experimentally investigate a wavelength-tunable fiber ring laser architecture by using the reflective semiconductor optical amplifier (RSOA) and semiconductor optical amplifier (SOA). Here, the wavelength tuning range from 1538.03 to 1561.91nm can be obtained. The measured output power and optical signal to noise ratio (OSNRs) of the proposed fiber laser are between -0.8 and -2.5 dBm and 59.1 and 61.0dB/0.06nm, respectively. The power and wavelength stabilities of the proposed laser are also studied. In addition, the proposed laser can be directly modulated at 2.5Gbit/s quadrature phase shift keying-orthogonal frequency-division multiplexing (QPSK-OFDM) signal and 20–50km single-mode fiber (SMF) transmissions are achieved within the forward error correction (FEC) limit without dispersion compensation. It could be a cost-effective and promising candidate for the standard-reach and extended-reach wavelength division multiplexed passive optical network (WDM-PON).

Noise beating in hybrid phase-sensitive amplifier systems

We investigate the effect of noise loading in a hybrid phase-sensitive amplifier system, analyzing the effect of noise beating between the signal and idler waves coupled in a parametric amplifier. Through analyzing input and output optical signal to noise ratios, we find that system performance of a phase-sensitive amplifier is 3 to 6 dB improved over a phase-insensitive amplifier, depending on the ratio of loaded noise power to that of vacuum fluctuations.

Signal-to-noise analysis in a counter-pumped fiber Raman amplifier

The light gain efficiency due to Raman scattering in a distributed fiber Raman amplifier is a subject of our investigation. The detailed analysis of noise properties at one-wave optical signal amplification in a single-mode fiber in the scheme of counter-pumped fiber Raman amplifier is realized in the paper. Experimental results of the amplified spontaneous emission with backward pumping as a base of optical noise evaluation are presented. Raman gain spectrum for a coherent Stokes low-powered signal is calculated and it is compared with the observed spectrum of non-coherent amplified spontaneous emission noise. It is shown that an output optical signal has higher gain than the amplified spontaneous emission and it results in the appreciable growth in the output optical signal-to-noise ratio.

The Transistor Laser: Theory and Experiment

The quantum-well (QW) heterojunction bipolar transistor (HBT) laser [the transistor laser (TL)], inherently a fast switching device, operates by transporting small minority base charge densities <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$\sim\!\! {\hbox {10}}^{16}\ {\hbox {cm}}^{-3}$</tex></formula> over nanoscale base thickness ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$&lt;$</tex></formula> 900 A) in picoseconds. The base QW acts as an optical “collector,” in addition to the usual electrical collector, that selects out “fast” recombining carriers, resulting in a short lifetime ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$\sim$</tex></formula> 29 ps) and higher differential laser gains. Charge and current continuity, together with the boundary conditions imposed by both collectors of the TL lead to a new charge control model, “unpinning” of population inversion beyond lasing threshold, quasi-Fermi level discontinuity across base QW, and a new equivalent circuit model requiring an extension to Kirchhoff's law. With the TL, the HBT becomes more than just a charge control device, but also a photon storage and switching device. The TL, owing to fast recombination speed, its unique three-terminal configuration, and the complementary nature of its optical and electrical collector output signals, enables resonance-free base current and collector voltage modulations, and compact realization of electro–optical applications such as nonlinear signal mixing, frequency multiplication, negative feedback, and optoelectronic logic gates.

A simple and accurate dynamical modeling of quantum-dot semiconductor optical amplifiers

SUMMARY In this article, quantum-dot semiconductor optical amplifiers (QD-SOAs) have been modelled using state space method. To derive this model, we have manipulated the rate equation model of the QD-SOA, where the average values of the occupation probabilities along the QD-SOA cavity are considered as the state variables of the system. Using these variables, the distance dependence of the rate equations is eliminated. The derived state space model gives the optical gain and output signal of the amplifier with a high accuracy. Simulation results show that the derived model is not only much simpler and faster than conventional rate equation models, but also the optical gain and output signal of the investigated QD-SOA are calculated with a higher precision compared to the rate equation model. Copyright © 2013 John Wiley & Sons, Ltd.

Coherent Wavelength Conversion in a Quantum Dot SOA

We experimentally demonstrate wavelength conversion of coherent signals in an InAs/InGaAsP/InP columnar quantum dot semiconductor optical amplifier by using low power single pump four-wave-mixing. We report highly efficient conversion, i.e., 30 nm conversion span with a conversion efficiency larger than -10 dB and output optical signal to noise ratio larger than 20 dB. Transparency to coherent modulation formats is demonstrated in a 25 nm conversion of 10 GBaud quadrature phase shift keying (QPSK), 8-phase shift keying (PSK) and 16-quadrature amplitude modulation (QAM) signals. We found 0.9 to 1.1 dB optical signal to noise ratio penalty at forward error correction error free limit of 2 × 10-3 bit error rate for all the signals.

A novel method degrading the combined effect of FWM and ASE noise in WDM systems containing in-line optical amplifiers

In this paper, a novel method degrading the combined effect of four-wave mixing (FWM) and amplified spontaneous emission (ASE) noise of the amplifier on the most heavily affected channel in an equally channel spaced wavelength division multiplexing (WDM) system containing in-line optical amplifiers is proposed. FWM effect is directly related to input powers of channels. So, FWM effect can be degraded by controlling channel input powers. In the proposed method, varying the input power of each channel in an optical fiber, the output optical signal to noise ratio (OSNR) values are evaluated and input powers of all channels are optimized in order to maximize the OSNR value of the channel having the lowest OSNR. To interpret the results obtained, output OSNR values for the minimum optical input power launched to the system by each channel are also computed. Being compared to the computed results for minimum optical input powers, the lowest output OSNR value among all channels for optimized input powers shows a 5.1867dB increase in a 5-channel system, a 3.5988dB increase in a 9-channel system, a 3.0855dB increase in a 15-channel system and a 1.6795dB increase for a 21-channel system. Furthermore, output OSNR values of all channels exhibit a significant increase.

The Application of Pseudo-Random Sequence in the Properties Measurement of Polymer Optical Fiber

A new method for the properties measurement of polymer optical fiber (POF) using pseudo-random sequence is introduced. The light source modulated by pseudo-random sequence is injected into the POF. The output optical signal after photoelectric conversion is made the correlation detection with pseudo-random sequence, and finally the correlation operation is carried out based on Labview software. Because pseudo-random sequence performs well on randomicity and it has the correlation properties similar to that of white noise, interference and noise have little influence on the peak of correlation function during the measurement, and the signal-to-noise ratio (SNR) of the output signal can be improved obviously. The measuring method is studied both theoretically and experimentally. Experimental results show that the SNR of the output signal can be improved by 25~40dB for the signal with SNR-15dB to 6dB, and the measuring precision is improved by this method.

A Closed-Loop Hydrogel-Based Chemical Sensor

State-of-the-art hydrogel-based chemical sensors directly convert the volume change of a hydrogel, induced by an external environmental chemical trigger such as pH, into an electrical or optical output signal. Because hydrogels show relaxation behavior and the network expansion is governed by slow cooperative diffusion, their long-term properties are poor and the sensor parameters, such as response time, are limited. To overcome these drawbacks, we present a closed-loop hydrogel-based pH sensor, which uses the compensation method. The hydrogel sensor itself is part of a feedback circuit comprising a proportional-integral controller and an actuator in the feedback loop. In our approach, the hydrogel volume is kept constant at the steady state during the whole measuring process. This is accomplished by applying an appropriate counter pressure that compensates the swelling pressure of the hydrogel and, thus, its attempt to swell or shrink. This counter pressure is a direct measure of the applied pH-value even though the hydrogel remains under isochoric conditions. Here, the novel closed-loop sensor approach and sensor technology are described, as well as measurement results that confirm the applicability of the compensation method to hydrogel sensors are shown.

三值光学计算机解码器的理论、技术和实现

In a ternary optical computer (TOC), the function of the decoder is to transform three-state optical signal output by the ternary optical processor into two-state electoral signals that can be used in an electronic computer. The coder has the inverse function. Together, the coder and decoder form a bridge for exchanging data between the TOC and an electronic computer. In the past decade, much research has focused on these two components in a TOC. As it has a simple structure, a favorable coder was manufactured in 2007. However, the complex mechanism of the decoder has improved more slowly. With the invention of the SD11, the third experimental TOC system for application research, most problems in the decoder were solved, new technologies were realized, and a theoretically better framework was introduced. In this paper we discuss these advancements in the TOC decoder. First, an ideal decoder structure abstracted from practice is shown in Figure 1. Next a suitable actual decoder comprising two camera modules and an embedded computer is illustrated in Figure 2. This is a simplification of the ideal structure and is used in the SD11. Thereafter, we describe the actual decoder's workflow, as depicted in Figure 3. Finally the use of and experiments with five key decoder techniques are discussed. The five techniques are address calibration, threshold setting, color correction, bad-pixels-out, and target picture judgment. Address calibration ascertains the memory address in the decode buffer for the data of every pixel in the target picture. The threshold setting ensures that each pixel's value is 1 when the pixel is brighter than the upper threshold and 0 when the pixel is darker than the lower threshold. Color correction removes the harmful effect from ambient light and the color cast of liquid crystal and Polaroid. Bad-pixels-out enforces substitutes for no-work pixels with spare work pixels, while target picture judgment accomplishes synchronization between the optical processor and decoder.

Directed xor/xnor Logic Gates Using U-to-U Waveguides and Two Microring Resonators

We propose and demonstrate a directed optical logic circuit, which can perform the XOR and XNOR logical operations based on U-to-U waveguides and two microring resonators. Compared to the previous structure, no waveguide crossings exist in the proposed circuit, which is beneficial to reduce the insertion loss and crosstalk of the device. Two electrical signals representing the two operands of the logical operation are employed to modulate two microring resonators through the thermo-optic effect, respectively. The operation result is represented by the output optical signal. For proof of principle, XOR and XNOR operations at 10 kb/s are demonstrated.

XOR/XNOR directed logic circuit based on coupled‐resonator‐induced transparency

AbstractThe coupled‐resonator‐induced transparency (CRIT) effect in parallel‐coupled double microring resonators (MRRs) has been widely studied, and various applications based on the CRIT have been demonstrated. As an application of the CRIT, we propose and demonstrate a directed logic circuit that can implement the XOR and XNOR operations. Two electrical signals applied to the two MRRs represent the two operands of the logical operations, and the operational results are represented by the output optical signal. As a proof‐of‐concept, the thermo‐optic modulating scheme is employed with an operational speed of 10 kbps.

Microwave Generation Based on Polarization Modulator and Brillouin-assisted Sideband-Filtering

A novel approach to generate continuously tunable microwave and millimeter-wave (mm-wave) signals is proposed and experimentally demonstrated. It is realized by a polarization modulator and a Brillouin-assisted sideband-filtering technique. The output optical signal of modulator is controlled to suppress the odd sidebands by a polarization controller and polarizer. After that, by adjusting the power of input microwave signal to remove the optical carrier, and then the strong second-order sideband of the modulated signal can be deeply suppressed by using stimulated Brillouin scattering (SBS) in a fiber ring while the fourth order sidebands keep unchanged. Therefore, only fourth-order sidebands signals exist at the input of the PD, frequency octupling can be realized. If the even sidebands are suppressed, the strong first order sidebands of the modulated signal will be deeply suppressed by the SBS filter, leaving the third sidebands, frequency sextupling can also be realized. As the SBS-assisted sideband-filter is narrow bandwidth and wavelength-independent, a wavelength-flexible way of optical generation mm-wave signals can be successfully realized.

Establishing a “Universal” Protein Biosensor Platform Based on FRagment Exchange (FREX) Mechanism

Biosensors couple binding events with a readily quantifiable optical output signal. Proteins are excellent recognition modules because of their inherent ability to bind ligands with high affinity and specificity. FRET is a powerful detection method because it can be ratiometric and genetically encoded. Researchers who wish to convert ordinary binding proteins into FRET-based biosensors are faced with two main challenges: (i) how to establish a binding-dependent conformational change, and (ii) how to make this change sufficiently large to produce robust FRET output. Here we develop the FRagment EXchange (FREX) methodology to address those two challenges. In the FREX approach, point mutations are introduced into the full-length parent protein to thermodynamically destabilize the protein and to knock out ligand binding. A polypeptide segment that covers both mutation sites, but contains the wild-type residues at those positions, is synthesized by partial sequence duplication of the parent protein. In the absence of ligand, the full-length protein is sufficiently stable to assume its native conformation. Addition of ligand induces a conformational change where a portion of the binding-incompetent full-length protein is swapped by the corresponding peptide. Ternary complex formation is driven by ligand binding energy and the gain in stability afforded by restoring wild-type side chain interactions. Placement of fluorescent reporter groups onto the full-length protein and the peptide fragment directly links ligand binding to a consistent and robust FRET increase. We demonstrate the method using the tenth human fibronectin type III domain (FN3), a versatile binding scaffold that has been previously modified to recognize a variety of targets. FREX establishes a customizable platform for a conformational switch in which ligand binding is coupled to a high-output reporter signal.

Dual-transduction-mode sensing approach for chemical detection

Abstract Smart devices such as electronic nose have been developed for application in many fields like national security, defense, environmental regulation, health care, pipeline monitoring and food analysis. Despite a large array of individual sensors, the resolving power of these devices can still be improved to identify a target at a very low concentration out of a mixture of odors, if different types of transductions are employed in concert as a set of sensing responses to distinguish one odor from another. Here, we propose a new sensor architecture enabling different types of transduction signals in parallel on the same individual sensor. We demonstrate this architecture using a light emitting organic field-effect transistor (LEOFET) operated at a dual-transduction mode, as a proof-of-concept. Sensing response has been observed on both electrical and optical output signals from a green LEOFET upon exposure to an explosive taggant, with optical signal exhibiting much higher sensitivity. This new sensor architecture opens a field of devices of synergic capabilities to distinguish chemical and biological targets.

Transistor laser optical and electrical linearity enhancement with collector current feedback

The three-port quantum well (QW) transistor laser (TL) is shown to provide a unique solution for generating ultra-linear electro-optical signals. With a simple collector current feedback loop, the 3rd order intermodulation distortion in the electrical and optical output signals of the transistor laser can be suppressed by as much 18.2 dB and 8.4 dB, respectively. These results show that the TL can be used for direct electro-optical feedback linearization, because of the base QW carrier-photon interaction, without incurring signal losses at multiple stages of auxiliary external electro-optical conversion circuitry.

Aminoanthraquinone-based chemosensors: colorimetric molecular logic mimicking molecular trafficking and a set–reset memorized device

The synthesis, photophysical properties, protonation and metal-ion coordination features of a family of four (3-6) anthraquinone-based schiff base derivatives are reported. The outstanding UV-vis absorption properties of the 1-aminoanthraquinone chromophore allowed the efficient visual detection and quantification of Cu(2+) and/or Ni(2+) in buffered aqueous solution. Analysis of spectrophotometric data with SPECFIT yielded the macroscopic and microscopic stability constants of the complexes. Furthermore, the different optical output signals (i.e. absorbance) observed with addition of various metal ions to a solution of 6 can be used for mimicking the operation of a traffic signal and "Set-Reset" molecular level information processing device.

Reduction of Interference Between pH and Optical Output Signals in a Multimodal Bio-Image Sensor

A low-interference multimodal sensor for pH and optical imaging has been developed. The interference signal that occurs between pH and the optical outputs is found to be caused by photogenerated electrons during pH sensing. This interference could be suppressed by adding another charge-accumulation region to a conventional multimodal sensor structure in order to measure only photogenerated electrons. Conventional pH sensing devices combine accumulation regions for photo generated electrons, thereby discriminating between pH and optical signals.