scholarly journals Optoelectronic mixer with a photoconductive switch for 1550 nm wavelengths

2018 ◽  
pp. 16-21
Author(s):  
Róbert Horváth ◽  
Jean-François Roux ◽  
Julien Poëtte ◽  
Béatrice Cabon
Keyword(s):  
Data Stream ◽  
Continuous Wave ◽  
Detection System ◽  
Local Oscillator ◽  
Optical Signal ◽  
Wide Frequency Range ◽  
Electrical Signal ◽  
Heterodyne Detection ◽  
Photoconductive Switch ◽  
Semiconductor Laser Diode

We demonstrate an optoelectronic mixer based on an ultrafast InGaAs photoconductive switch and its use in an innovative heterodyne detection system for Radio over Fibre transmission. The advantage of the proposed switch is its relatively flat response curve in a wide frequency range up to 67 GHz. Two mixing schemes are presented through I-Q modulated data-stream down-conversion. The data can modulate either the electrical signal or the optical signal. In case the electrical signal is modulated, a mode-locked semiconductor laser diode is used as an optical local oscillator at the self-oscillating frequency of 24.5 GHz. The InP based quantum-dash mode-locked laser emitting in the 1570 nm wavelength range is stabilized by a feedback loop and shows a low phase noise in order to increase the mixing performances of the detection apparatus. In a second experiment, the photoconductive switch is combined with a continuous wave laser to demonstrate the feasibility of down converting an optically provided data-stream with an electrical local oscillator.

Télémètre à détection coherente avec un laser CO2 à ondes entretenues : étude et conception

1983 ◽  
Vol 61 (2) ◽  
pp. 318-331 ◽  
Author(s):  
Denis Vincent ◽  
Gabriel Otis
Keyword(s):  
Detection System ◽  
Signal To Noise Ratio ◽  
Optical Power ◽  
Experimental System ◽  
Intermediate Frequency ◽  
Local Oscillator ◽  
Heterodyne Detection ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Rotating Target

We performed a theoretical and experimental study of a 10.6 μm heterodyne detection system with nonlinear postdetection. A single laser serves as both transmitter and local oscillator; the intermediate frequency is given by the Doppler effect due to a rotating target. An electrooptic crystal modulates the amplitude of the laser beam at a frequency of 15 kHz; a synchronous voltmeter measures the return signal after the nonlinear element. Values of the signal-to-noise ratio with respect to incident optical power agree with the results of the theoretical model. In particular, experimentally measured target-induced frequency spreading effects on the signal-to-noise ratio correspond to the predictions of the model. We also describe an experimental system.

scholarly journals Implementation of Optical Coherent Communication System between Two Computers

2010 ◽  
Vol 7 (1) ◽  
pp. 41-47
Author(s):  
Baghdad Science Journal
Keyword(s):  
Optical Fiber ◽  
Communication System ◽  
Signal To Noise Ratio ◽  
Single Mode ◽  
Local Oscillator ◽  
Optical Signal ◽  
Coherent Detection ◽  
Heterodyne Detection ◽  
Laser Source ◽  
Coherent Communication

This work represents implementation and investigation of optical coherent communication system between two computers. A single mode optical fiber is selected as transmission medium. The data are sent via the RS-232 standard interface with a bit rate of 9.6 kbps from personal computer (PC1) by line receive to convert the data from electrical levels (-12/+12 V) into TTL level (0/5 V). The modulation of this data was accomplished by internal modulation using laser diode type (HFCT-5208M) 1310 nm wavelength. The optical D-coupler was used to combine the optical signal that come from laser source with optical signal of laser local oscillator (OTS-304XI) at 1310/1550 nm wavelength to obtain coherent (homodyne and heterodyne) detection respectively. A PIN photodetector (HFCT-5208M) is used. Calculations of Signal to Noise Ratio (SNR) and Bit Error Rate (BER) for coherent detection were measured at different length of the optical fiber. Result show that high SNR and low BER for heterodyne detection than for homodyne detection.

scholarly journals Heterodyne sensing of microwaves with a quantum sensor

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jonas Meinel ◽  
Vadim Vorobyov ◽  
Boris Yavkin ◽  
Durga Dasari ◽  
Hitoshi Sumiya ◽  
...  
Keyword(s):  
Spectral Resolution ◽  
Detection Method ◽  
Local Oscillator ◽  
Wide Frequency Range ◽  
Heterodyne Detection ◽  
High Spectral Resolution ◽  
Superposition State ◽  
Frequency Range ◽  
Future Studies ◽  
Microwave Signals

AbstractDiamond quantum sensors are sensitive to weak microwave magnetic fields resonant to the spin transitions. However, the spectral resolution in such protocols is ultimately limited by the sensor lifetime. Here, we demonstrate a heterodyne detection method for microwaves (MW) leading to a lifetime independent spectral resolution in the GHz range. We reference the MW signal to a local oscillator by generating the initial superposition state from a coherent source. Experimentally, we achieve a spectral resolution below 1 Hz for a 4 GHz signal far below the sensor lifetime limit of kilohertz. Furthermore, we show control over the interaction of the MW-field with the two-level system by applying dressing fields, pulsed Mollow absorption and Floquet dynamics under strong longitudinal radio frequency drive. While pulsed Mollow absorption leads to improved sensitivity, the Floquet dynamics allow robust control, independent from the system’s resonance frequency. Our work is important for future studies in sensing weak microwave signals in a wide frequency range with high spectral resolution.

USE OF A CO2LASER AS A LOCAL OSCILLATOR FOR A 10 MICRON HETERODYNE DETECTION

1987 ◽  
Vol 48 (C7) ◽  
pp. C7-569-C7-571
Author(s):  
A. DELAHAIGUE ◽  
D. COURTOIS ◽  
C. THIEBEAUX ◽  
H. LE CORRE
Keyword(s):  
Local Oscillator ◽  
Heterodyne Detection

scholarly journals A Local Oscillator Phase Compensation Technique for Ultra-Wideband Stepped-Frequency Continuous Wave Radar Based on a Low-Cost Software-Defined Radio

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 780
Author(s):  
Kazunori Takahashi ◽  
Takashi Miwa
Keyword(s):  
Software Defined Radio ◽  
Initial Phase ◽  
Continuous Wave ◽  
Low Cost ◽  
Local Oscillator ◽  
The Other ◽  
Ultra Wideband ◽  
Single Frequency ◽  
Wave Radar ◽  
Stepped Frequency

The paper discusses a way to configure a stepped-frequency continuous wave (SFCW) radar using a low-cost software-defined radio (SDR). The most of high-end SDRs offer multiple transmitter (TX) and receiver (RX) channels, one of which can be used as the reference channel for compensating the initial phases of TX and RX local oscillator (LO) signals. It is same as how commercial vector network analyzers (VNAs) compensate for the LO initial phase. These SDRs can thus acquire phase-coherent in-phase and quadrature (I/Q) data without additional components and an SFCW radar can be easily configured. On the other hand, low-cost SDRs typically have only one transmitter and receiver. Therefore, the LO initial phase has to be compensated and the phases of the received I/Q signals have to be retrieved, preferably without employing an additional receiver and components to retain the system low-cost and simple. The present paper illustrates that the difference between the phases of TX and RX LO signals varies when the LO frequency is changed because of the timing of the commencement of the mixing. The paper then proposes a technique to compensate for the LO initial phases using the internal RF loopback of the transceiver chip and to reconstruct a pulse, which requires two streaming: one for the device under test (DUT) channel and the other for the internal RF loopback channel. The effect of the LO initial phase and the proposed method for the compensation are demonstrated by experiments at a single frequency and sweeping frequency, respectively. The results show that the proposed method can compensate for the LO initial phases and ultra-wideband (UWB) pulses can be reconstructed correctly from the data sampled by a low-cost SDR.

scholarly journals Laser spectroscopy of the $$^2{\mathrm{S}}_{1/2}{-}^2{\mathrm{P}}_{{1}/2}$$, $$^2{\mathrm{P}}_{3/2}$$ transitions in stored and cooled relativistic C$$^{3+}$$ ions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
D. Winzen ◽  
V. Hannen ◽  
M. Bussmann ◽  
A. Buß ◽  
C. Egelkamp ◽  
...  
Keyword(s):  
Laser Spectroscopy ◽  
Continuous Wave ◽  
Detection System ◽  
Laser System ◽  
Theoretical Data ◽  
Plasma Spectroscopy ◽  
Carbon Ions ◽  
Uv Laser ◽  
Spectroscopy Experiment ◽  
Extreme Uv

AbstractThe $$^2{\mathrm{S}}_{1/2}{-}^2{\mathrm{P}}_{{1}/2}$$ 2 S 1 / 2 - 2 P 1 / 2 and $$^2{\mathrm{S}}_{1/2}{-}^2{\mathrm{P}}_{{3}/2}$$ 2 S 1 / 2 - 2 P 3 / 2 transitions in Li-like carbon ions stored and cooled at a velocity of $$\beta \approx 0.47$$ β ≈ 0.47 in the experimental storage ring (ESR) at the GSI Helmholtz Centre in Darmstadt have been investigated in a laser spectroscopy experiment. Resonance wavelengths were obtained using a new continuous-wave UV laser system and a novel extreme UV (XUV) detection system to detect forward emitted fluorescence photons. The results obtained for the two transitions are compared to existing experimental and theoretical data. A discrepancy found in an earlier laser spectroscopy measurement at the ESR with results from plasma spectroscopy and interferometry has been resolved and agreement between experiment and theory is confirmed.

Fall Detection via Inaudible Acoustic Sensing

2021 ◽  
Vol 5 (3) ◽  
pp. 1-21
Author(s):  
Jie Lian ◽  
Xu Yuan ◽  
Ming Li ◽  
Nian-Feng Tzeng
Keyword(s):  
Continuous Wave ◽  
Detection System ◽  
Fall Detection ◽  
Superior Performance ◽  
Medical Assistance ◽  
Acoustic Sensing ◽  
Value Decomposition ◽  
Human Motions ◽  
Audio Device ◽  
Fall Accidents

The fall detection system is of critical importance in protecting elders through promptly discovering fall accidents to provide immediate medical assistance, potentially saving elders' lives. This paper aims to develop a novel and lightweight fall detection system by relying solely on a home audio device via inaudible acoustic sensing, to recognize fall occurrences for wide home deployment. In particular, we program the audio device to let its speaker emit 20kHz continuous wave, while utilizing a microphone to record reflected signals for capturing the Doppler shift caused by the fall. Considering interferences from different factors, we first develop a set of solutions for their removal to get clean spectrograms and then apply the power burst curve to locate the time points at which human motions happen. A set of effective features is then extracted from the spectrograms for representing the fall patterns, distinguishable from normal activities. We further apply the Singular Value Decomposition (SVD) and K-mean algorithms to reduce the data feature dimensions and to cluster the data, respectively, before input them to a Hidden Markov Model for training and classification. In the end, our system is implemented and deployed in various environments for evaluation. The experimental results demonstrate that our system can achieve superior performance for detecting fall accidents and is robust to environment changes, i.e., transferable to other environments after training in one environment.

scholarly journals Active Optical Signal Conditioning and Monitoring System

2021 ◽  
Author(s):  
Kalipada Chatterjee ◽  
Subrat Sahu ◽  
Venugopal Arumuru ◽  
Rajan jha
Keyword(s):  
Real Time ◽  
Signal To Noise Ratio ◽  
Optical Signal ◽  
Wide Frequency Range ◽  
Optical Systems ◽  
Signal Conditioning ◽  
Time Modulation ◽  
Response Enhancement ◽  
Signal Monitoring ◽  
External Stimuli

Abstract An optical signal conditioning technique for dynamic modulation of signals and real-time monitoring of events is pivotal for developing various optical systems at micro/nano dimensions. The utilities of such technique include controllable signal enhancement and distinctive response towards external stimuli, with reconfigurable operational range. Here, we propose and demonstrate an optical technique based on the parallel integration of fiber modal interferometers for optical response enhancement and multi-signal monitoring. Overlap of the interferometers’ characteristic spectra facilitates controllable signal filtering, attenuation, and amplification of interferometer’s response towards dynamic field over wide frequency range of 1 Hz – 1 kHz. Signal to noise ratio (SNR) enhancement of 9 dB is achieved by applying 1 volt about the reference interferometer. The system enables real-time modulation of optical signals and multipoint signal monitoring using machine learning for various applications such as mechanical vibrations, acoustic fields, biological samples, fluid movement, and other similar dynamic fields.

Life signals detection system based on a continuous‐wave X‐band radar

2016 ◽  
Vol 52 (23) ◽  
pp. 1903-1904 ◽  
Author(s):  
M. Donelli ◽  
F. Viani
Keyword(s):  
Continuous Wave ◽  
Detection System ◽  
X Band
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