scholarly journals Effect of the APD Receiver’s Tilted Angle on Channel Capacity for Underwater Wireless Optical Communications

Electronics ◽  
2021 ◽  
Vol 10 (18) ◽  
pp. 2246
Author(s):  
Meiyan Ju ◽  
Hongqiang Shi ◽  
Yueheng Li ◽  
Ping Huang ◽  
Guoping Tan
Keyword(s):  
Channel Capacity ◽  
Lower Bounds ◽  
Peak Power ◽  
Average Power ◽  
Avalanche Photodiode ◽  
Tilted Angle ◽  
Wireless Optical Communication ◽  
Wireless Optical Communications ◽  
Simple Convex ◽  
Capacity Performance

This paper focuses on investigating the effect of the receiver’s tilted angle on the channel capacity of an underwater wireless optical communication (UWOC) system, in which an avalanche photodiode (APD) detector is adopted as the receiver. Under the non-negativity, peak power, and average power constraints, the lower bounds on the capacity of UWOC are derived in detail according to different average-to-peak power ratios. With modeling achieving the maximum of the lower bounds of the capacity as an optimization object, we prove that the proposed optimization issue is in fact a simple convex optimization about the tilted angle of the APD receiver, and then present related theoretical solution for it. Both theoretical analysis and simulation results show that by appropriately tilting the receiver, we can significantly enhance the final capacity performance of the UWOC with APD receiver.

scholarly journals An Eye-Safe, SBS-Free Coherent Fiber Laser LIDAR Transmitter with Millijoule Energy and High Average Power

Photonics ◽  
2021 ◽  
Vol 8 (1) ◽  
pp. 15
Author(s):  
Mehmetcan Akbulut ◽  
Leonid Kotov ◽  
Kort Wiersma ◽  
Jie Zong ◽  
Maohe Li ◽  
...  
Keyword(s):  
Fiber Laser ◽  
Repetition Rate ◽  
Peak Power ◽  
Figure Of Merit ◽  
Current System ◽  
Glass Fibers ◽  
Average Power ◽  
High Gain ◽  
Short Length ◽  
High Average Power

We report on an eye-safe, transform-limited, millijoule energy, and high average power fiber laser. The high gain and short length of the NP phosphate-glass fibers enable the SBS-free operation with kW level peak power. The output energy is up to 1.3 mJ, and the average power is up to 23 W at an 18 kHz repetition rate with 600 ns pulses (peak power > 2.1 kW). The PER is ≈16 dB and the M2 of the beam is 1.33 × 1.18. The coherent LIDAR Figure Of Merit (FOM) is 174 mJ*sqrt(Hz), which to our knowledge is the highest reported for a fiber laser. We also report 0.75 mJ energy and >3.7 kW peak power with down to 200 ns pulses and up to 1.21 mJ energy with a 3–5 kHz repetition rate operation of the current system.

Performance of LED for line-of-sight (LoS) underwater wireless optical communication system

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Alaa G. Nasser ◽  
Mazin Ali A. Ali
Keyword(s):  
Optical Communication ◽  
Link Quality ◽  
Line Of Sight ◽  
Modulation Scheme ◽  
Underwater Communication ◽  
Optical Communication System ◽  
High Data ◽  
Wireless Optical Communication ◽  
Noise Rate ◽  
Wireless Optical Communications

AbstractUnderwater wireless optical communications (UWOC) recently emerge as a solution to the problem of underwater communication for link with a high data rate, low delay, safety, and high immunity. In this study, the line of sight (LoS) method based on LED used for UWOC with different modulation schemes. The bit error rate (BER), signal-to-noise rate, and quality factor are used for assessing system performance and link quality. Besides the effect of transmitting angle, distance link (d), and transmitting power (PT) are analysed. Results show that 8-pulse position modulation (PPM) is the best modulation scheme for achieving a good link in the LoS method.

Stable continuous-wave mode-locked laser from a 1645 nm Er:YAG ceramic oscillator

2022 ◽  
Author(s):  
Yangyu Liu ◽  
Xue Cao ◽  
AnHua Xian ◽  
Guangmiao Liu ◽  
Wei zhou ◽  
...  
Keyword(s):  
Solid State ◽  
Pulse Width ◽  
Peak Power ◽  
Continuous Wave ◽  
Modulation Depth ◽  
Average Power ◽  
Mode Locking ◽  
Wave Mode ◽  
Semiconductor Saturable Absorber ◽  
Continuous Wave Mode

Abstract We demonstrate stable continuous-wave mode-locking (CWML) pulses around 1645nm by employing the home-made Er:YAG ceramic. By using a fiber laser and semiconductor saturable absorber mirror (SESAM) with modulation depth of 1.2%, we get ML pulses with the output average power up to 815 mW, the pulse width shortened as ~4 ps, and the peak power of 1.8 kW. With the SESAM of modulation depth of 2.4%, the second-order harmonic ML pulses were also obtained. As far as we know, this is the first report of CWML from Er3+-doped ceramics and also the shortest pulse duration in Er3+-doped solid-state oscillators.

Catchlike-inducing train activation of human muscle during isotonic contractions: burst modulation

1999 ◽  
Vol 87 (5) ◽  
pp. 1758-1767 ◽  
Author(s):  
Samuel C. K. Lee ◽  
Cara N. Becker ◽  
Stuart A. Binder-Macleod
Keyword(s):  
Isometric Contraction ◽  
Peak Power ◽  
Average Power ◽  
Knee Extension ◽  
Human Muscle ◽  
Constant Frequency ◽  
Maximum Voluntary Isometric Contraction ◽  
Before And After ◽  
Isotonic Performance ◽  
Isotonic Contractions

Stimulation trains that exploit the catchlike property [catchlike-inducing trains (CITs)] produce greater forces and rates of rise of force than do constant-frequency trains (CFTs) during isometric contractions and isovelocity movements. This study examined the effect of CITs during isotonic contractions in healthy subjects. Knee extension was electrically elicited against a load of 10% of maximum voluntary isometric contraction. The stimulation intensity was set to produce 20% of maximum voluntary isometric contraction. The muscle was tested before and after fatigue with a 6-pulse CFT and 6-pulse CITs that contained an initial doublet, triplet, or quadruplet. For prefatigue responses, the greatest isotonic performance was produced by CITs with initial doublets. When the muscles were fatigued, triplet CITs were best. CITs produce greater excursion, work, peak power, and average power than do CFTs, because CITs produced more rapid rates of rise of force. Faster rates of rise of force enabled the preload on the muscle to be exceeded earlier during the stimulation train.

scholarly journals Quasi-Parametric Chirped-Pulse Amplification Simultaneously Enables High Peak Power and High Average Power

2019 ◽  
Vol 11 (4) ◽  
pp. 1-12 ◽  
Author(s):  
Zhe Yin ◽  
Jingui Ma ◽  
Jing Wang ◽  
Peng Yuan ◽  
Guoqiang Xie ◽  
...  
Keyword(s):  
Peak Power ◽  
Average Power ◽  
High Peak ◽  
High Peak Power ◽  
High Average Power ◽  
Chirped Pulse ◽  
Pulse Amplification ◽  
Chirped Pulse Amplification

71 W Average Power Sub-MW Peak Power Diffraction-Limited Monolithic Tapered Fiber Amplifier

2019 ◽  
Author(s):  
Konstantin K. Bobkov ◽  
Mikhail E. Likhachev ◽  
Andrey E. Levchenko ◽  
Vladimir V. Velmiskin ◽  
Tatyana A. Kochergina ◽  
...  
Keyword(s):  
Peak Power ◽  
Average Power ◽  
Fiber Amplifier ◽  
Tapered Fiber

A constant-load ergometer for measuring peak power output and fatigue

1988 ◽  
Vol 65 (5) ◽  
pp. 2343-2348 ◽  
Author(s):  
J. H. Williams ◽  
W. S. Barnes ◽  
J. F. Signorile
Keyword(s):  
Power Output ◽  
Peak Power ◽  
Intraclass Correlation ◽  
Average Power ◽  
Load Cycle ◽  
Constant Load ◽  
Load Cell ◽  
Peak Power Output ◽  
Maximal Power Output ◽  
Power Curves

A constant-load cycle ergometer was constructed that allows maximal power output to be measured for each one-half pedal revolution during brief, high-intensity exercise. To determine frictional force, an electronic load cell was attached to the resistance strap and the ergometer frame. Dead weights were attached to the strap's free end. Flywheel velocity was recorded by means of a magnetic switch and two magnets placed on the pedal sprocket. Pedaling resulted in magnetically activated switch closures, which produced two electronic pulses per pedal revolution. Pulses and load cell output were recorded (512 Hz), digitized, and stored on disk via microcomputer. Power output was later computed for each pair of adjacent pulses, representing average power per one-half pedal revolution. Power curves generated for each subject were analyzed for peak power output (the highest one-half pedal revolution average), time to peak power, power fatigue rate and index, average power, and total work. Thirty-eight males performed two 15-s tests separated by 15 min (n = 16) or 48 h (n = 22). Peak power output ranged from 846.0 to 1,289.1 W. Intraclass correlation analysis revealed high test-retest reliability for all parameters recorded on the same or different days (R = 0.91-0.97). No significant differences (P greater than 0.05) were noted between parameter means of the first and second tests. These results indicate that the ergometer described provides a means for conveniently and reliably assessing short-term power output and fatigue.

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