scholarly journals Carrier-Assisted Phase Retrieval

2021 ◽  
Author(s):  
Qi Wu
Keyword(s):  
Phase Retrieval ◽  
Forward Error Correction ◽  
Signal To Noise Ratio ◽  
Single Mode ◽  
Local Oscillator ◽  
Optical Signal ◽  
Single Mode Fiber ◽  
Critical Parameters ◽  
Hardware Complexity ◽  
Full Field

Phase-retrieval (PR) schemes based on the modified Gerchberg-Saxton (GS) algorithm capture the full-field employing a dispersive element and intensity-only measurements to eliminate the use of a local oscillator. In this work, we propose two carrier-assisted PR schemes, namely central carrier-assisted PR (CCA-PR) and edge carrier-assisted PR (ECA-PR), to improve the comprehensive performance of PR receiver in terms of convergence speed, redundancy, and computational complexity. The proposed CCA-PR recovers the electrical field employing a reference carrier at 0 GHz with several iterations between two projection planes. It avoids pilot symbols and digital backpropagation to the transmitter and offers a flexible electrical bandwidth requirement compared with conventional PR schemes. To lower the carrier-to-signal power ratio (CSPR) requirement and enable faster convergence for the carrier-assisted PR schemes, the ECA-PR is proposed to obtain the initial phase for the GS algorithm. We numerically characterize the performance of the two schemes and experimentally demonstrate them for 30 GBaud 16-quadrature amplitude modulation (16-QAM) transmission over 80 km single-mode fiber with a bit error rate (BER) below the threshold of 7% hard-decision forward error correction (HD-FEC). Several critical parameters are analyzed, including the applied dispersion value, CSPR, and electrical bandwidth. Moreover, we compare the hardware complexity and optical signal-to-noise ratio (OSNR) sensitivity of proposed PR schemes with mainstream field recovery schemes.

scholarly journals Carrier-Assisted Phase Retrieval

2021 ◽  
Author(s):  
Qi Wu
Keyword(s):  
Phase Retrieval ◽  
Forward Error Correction ◽  
Signal To Noise Ratio ◽  
Single Mode ◽  
Local Oscillator ◽  
Optical Signal ◽  
Single Mode Fiber ◽  
Critical Parameters ◽  
Hardware Complexity ◽  
Full Field

Phase-retrieval (PR) schemes based on the modified Gerchberg-Saxton (GS) algorithm capture the full-field employing a dispersive element and intensity-only measurements to eliminate the use of a local oscillator. In this work, we propose two carrier-assisted PR schemes, namely central carrier-assisted PR (CCA-PR) and edge carrier-assisted PR (ECA-PR), to improve the comprehensive performance of PR receiver in terms of convergence speed, redundancy, and computational complexity. The proposed CCA-PR recovers the electrical field employing a reference carrier at 0 GHz with several iterations between two projection planes. It avoids pilot symbols and digital backpropagation to the transmitter and offers a flexible electrical bandwidth requirement compared with conventional PR schemes. To lower the carrier-to-signal power ratio (CSPR) requirement and enable faster convergence for the carrier-assisted PR schemes, the ECA-PR is proposed to obtain the initial phase for the GS algorithm. We numerically characterize the performance of the two schemes and experimentally demonstrate them for 30 GBaud 16-quadrature amplitude modulation (16-QAM) transmission over 80 km single-mode fiber with a bit error rate (BER) below the threshold of 7% hard-decision forward error correction (HD-FEC). Several critical parameters are analyzed, including the applied dispersion value, CSPR, and electrical bandwidth. Moreover, we compare the hardware complexity and optical signal-to-noise ratio (OSNR) sensitivity of proposed PR schemes with mainstream field recovery schemes.

scholarly journals Microdrilled tapers to enhance optical fiber lasers for sensing

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
R. A. Perez-Herrera ◽  
M. Bravo ◽  
P. Roldan-Varona ◽  
D. Leandro ◽  
L. Rodriguez-Cobo ◽  
...  
Keyword(s):  
Optical Fiber ◽  
Optical Fibers ◽  
Fiber Lasers ◽  
Signal To Noise Ratio ◽  
Power Level ◽  
Single Mode ◽  
Optical Signal ◽  
Single Mode Fiber ◽  
Output Power Level ◽  
Linear Cavity

AbstractIn this work, an experimental analysis of the performance of different types of quasi-randomly distributed reflectors inscribed into a single-mode fiber as a sensing mirror is presented. These artificially-controlled backscattering fiber reflectors are used in short linear cavity fiber lasers. In particular, laser emission and sensor application features are analyzed when employing optical tapered fibers, micro-drilled optical fibers and 50 μm-waist or 100 μm-waist micro-drilled tapered fibers (MDTF). Single-wavelength laser with an output power level of about 8.2 dBm and an optical signal-to-noise ratio of 45 dB were measured when employing a 50 μm-waist micro-drilled tapered optical fiber. The achieved temperature sensitivities were similar to those of FBGs; however, the strain sensitivity improved more than one order of magnitude in comparison with FBG sensors, attaining slope sensitivities as good as 18.1 pm/με when using a 50 μm-waist MDTF as distributed reflector.

Efficient Blind Adaptive CSE to Reduce Cyclic Prefix Length in Direct Detection Optical OFDM Systems

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
Asmaa Benieddi ◽  
Sid Ahmed Elahmar
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Direct Detection ◽  
Group Velocity Dispersion ◽  
Signal To Noise Ratio ◽  
Single Mode ◽  
Optical Signal ◽  
Single Mode Fiber ◽  
Cyclic Prefix ◽  
Ofdm Systems ◽  
Blind Adaptive

AbstractDirect detection optical orthogonal frequency division multiplexing (DDO-OFDM) systems for a long-reach of standard single mode fiber (SSMF) require a large length of cyclic prefix (CP) to avoid the inter-symbol interference (ISI) effect caused by group velocity dispersion (GVD). Unfortunately, this method is inefficient due to the energy wasted in CP samples. In order to reduce the CP length and to mitigate the residual ISI, a novel blind adaptive channel shortening equalizer (CSE) is proposed in this paper. Based on the orthogonality between subcarriers in the fast Fourier transform (FFT) property, the proposed algorithm attempts to minimize the sum-squared correlation (SSCM) between each sample located in a well-defined window to update the CSE coefficients. Thus, the combined channel-CSE response is shortened. Therefore, it can cancel the residual ISI effect due to the GVD and the short CP length. The performance of the system is evaluated on basis of bit error rate (BER) versus optical signal to noise ratio (OSNR) for different CP lengths. The simulation results validate the new algorithm SSCM and show that it can reduce the CP length with a much better system improvement than existing algorithms.

Analysis of secured Optical Orthogonal Frequency Division Multiplexed System

2017 ◽  
Vol 38 (2) ◽  
Author(s):  
Harsimranjit Singh Gill ◽  
Kamaljit Singh Bhatia ◽  
Sandeep Singh Gill
Keyword(s):  
Signal To Noise Ratio ◽  
Average Power ◽  
Single Mode ◽  
Optical Signal ◽  
Data Encryption ◽  
Single Mode Fiber ◽  
Frequency Division ◽  
Ofdm Systems ◽  
Ofdm Signal ◽  
Coded Ofdm

AbstractIn this paper, security issues for optical orthogonal frequency division multiplexed (OFDM) systems are emphasized. The encryption has been done on the data of coded OFDM symbols using data encryption standard (DES) algorithm before transmitting through the fiber. The results obtained justify that the DES provides better security to the input data without further bandwidth requirement. The data is transmitted to a distance of 1,000 km in a single-mode fiber with 16-quadrature amplitude modulation. The peak-to-average power ratio and optical signal-to-noise ratio of secure coded OFDM signal is fairly better than the conventional OFDM signal.

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 A Theoretical Study and Numerical Simulation of a Quasi-Distributed Sensor Based on the Low-Finesse Fabry-Perot Interferometer: Frequency-Division Multiplexing

2017 ◽  
Author(s):  
José Trinidad Guillen Bonilla ◽  
Alex Guillén-Bonilla ◽  
Rodríguez-Betancourtt Veronica M. ◽  
Héctor Guillen Bonilla ◽  
Antonio Casillas Zamora
Keyword(s):  
Optical Fiber ◽  
Frequency Domain ◽  
Signal To Noise Ratio ◽  
Single Mode ◽  
Optical Signal ◽  
Single Mode Fiber ◽  
Wavelength Shift ◽  
Distributed Sensors ◽  
Distributed Sensor ◽  
Fabry Perot

The application of the sensors optical fiber in the areas of scientific instrumentation and industrial instrumentation is very attractive due to its numerous advantages. In the industry of civil engineering for example, quasi-distributed sensors made with optical fiber are used for reliable strain and temperature measurements. Here, a quasi-distributed sensor in the frequency domain is discussed. The sensor consists of a series of low-finesse Fabry-Perot interferometers where each Fabry-Perot interferometer acts as a local sensor. Fabry-Perot interferometers are formed by pairs of identical low reflective Bragg gratings imprinted in a single mode fiber. All interferometer sensors have different cavity length, provoking the frequency-domain multiplexing. The optical signal represents the superposition of all interference patterns which can be decomposed using the Fourier transform. The frequency spectrum is analyzed and sensor´s properties were defined. Following, a quasi-distributed sensor was numerically simulated. Our sensor simulation considers sensor properties, signal processing, noise system and instrumentation. The numerical results show the behavior of resolution vs. signal-to-noise ratio. From our results, the Fabry-Perot sensor has high resolution and low resolutions. Both resolutions are conceivable because the FDPA algorithm elaborates two evaluations of Bragg wavelength shift

Switchable and tunable linear cavity erbium-doped fiber laser based on FBGs embedded in Sagnac rings

Laser Physics ◽  
2021 ◽  
Vol 32 (1) ◽  
pp. 015101
Author(s):  
Gangxiao Yan ◽  
Weihua Zhang ◽  
Peng Li ◽  
Qiuhao Jiang ◽  
Meng Wu ◽  
...  
Keyword(s):  
Fiber Laser ◽  
Low Cost ◽  
Single Mode ◽  
Optical Signal ◽  
Single Mode Fiber ◽  
Hole Burning ◽  
Linear Cavity ◽  
Erbium Doped ◽  
Optical Fiber Sensing ◽  
Birefringence Effect

Abstract A switchable and tunable erbium-doped fiber laser with a linear cavity based on fiber Bragg gratings embedded in Sagnac rings is proposed and experimentally verified. Due to the stress birefringence effect and the polarized hole burning effect, which are introduced into the single-mode fiber in the polarization controllers (PCs) by the PCs, the designed laser can achieve seven kinds of laser-states output including three kinds of single-wavelength laser states, three kinds of dual-wavelength laser states and one kind of triple-wavelength laser state. The optical signal-to-noise ratios of the output wavelengths are all higher than 52 dB, and the wavelength shifts are all less than 0.04 nm. Furthermore, the temperature tuning of the wavelength range is also researched, which is about 1.2 nm. Due to advantages, such as low cost, simple structure, easy switching and multiple laser states, the designed laser has great application potential in laser radar, optical fiber sensing and so on.

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