Junhao Hu

Nanotube Q-switched low-threshold linear cavity tunable erbium-doped fiber laser

We demonstrate a novel all-fiber nanotube Q-switched low-threshold linear cavity tunable erbium-doped fiber laser (EDFL). With a compact and low insertion loss carbon nanotube based saturable absorber connected in a linear EDFL cavity, a low pump threshold of 18.57mW is obtained. The pulse repetition rate can be adjusted from 8.12 to 72.2kHz by varying the pump power from 18.57 to 118.8mW. In addition, the emission wavelength can be adjusted from 1545.04 to 1549.99nm by tuning the central wavelength of the fiber Bragg grating, which serves as an end mirror of the laser cavity.

Wideband-tunable nanotube Q-switched low threshold erbium doped fiber laser

An all-fiber passively wideband-tunable nanotube Q-switched low threshold erbium doped fiber laser is presented. With a low insertion loss carbon nanotube based saturable absorber, C- and L-band tunable Q-switched lasers are achieved by tuning the transmission wavelength of one C-band tunable filter and the other L-band one, respectively. The threshold of the Q-switched operation is only 12.8 mW. The self-mode-locking effect on the Q-switching can be effectively reduced by introducing a spatial hole burning effect with two optical circulators. The tunable wavelength range of the Q-switching laser can be changed by inserting a variable optical attenuator in the laser cavity to tune the gain spectrum.

Wide Pulse-Repetition-Rate Range Tunable Nanotube

A novel all-fiber wide pulse-repetition-rate range tunable nanotube Q-switched low threshold erbium-doped fiber (EDF) laser is demonstrated. By connecting a compact and low insertion loss carbon nanotube-based saturable absorber and a section of high concentration EDF in a simple linear laser cavity, Q-switched laser, with a threshold of 29.85 mW, a pulse-repetition-rate tunable range of 14.5-141.4 kHz, and a minimum pulse duration of 330 ns, are achieved. With this laser structure, the self-mode-locking effect on the Q-switch operation can be effectively suppressed.

Q

A simple 100-km long distance fiber Bragg grating sensor system was proposed and demonstrated. It can achieve 100-km measurement length with reflected Bragg wavelength spectrum of 30 dB signal noise ratio by using only one Raman pump laser source with 1 W power at 1395 nm and two segments of erbium-doped fiber at the locations of 50 and 75 km separately.

-Switched Low Threshold Erbium-Doped Fiber Laser

A 150-km long distance fiber Bragg Grating (FBG) temperature and vibration sensor system was proposed and demonstrated by using the stimulated Raman amplification. It can achieve 150-km measurement range by using a low power 1480-nm laser as the Stokes of the pump laser at 1395 nm in the progress of stimulated Raman amplification. And the whole system only consist one Raman pump laser source with 1-W power at 1395 nm, a low-power 1480-nm laser and two segments of erbium doped fiber (EDF) at the location of 50 km and 75 km separately.

100-km Long Distance Fiber Bragg Grating Sensor System Based on Erbium-Doped Fiber and Raman Amplification

We proposed a new RGB coding method in LED/LCD-camera communication link to increase the transmission rate by 3 times. The prototype of our system can achieve 1.5 meter transmission distance with up to 450 Kbit/s transmission rate. The relationship between transmission rate and distance, stabilization effects are also studied in detail to illustrate the advantage and limitation of this system.

150-km Long Distance FBG Temperature and Vibration Sensor System Based on Stimulated Raman Amplification

In this paper, we summarize our recent research work on two types of optical fiber sensors: long distance sensor and biomedical sensor. For long distance sensing, we demonstrated our 150-km long distance fiber Bragg Grating (FBG) temperature and vibration sensor system and Brillouin optical time domain analysis distributed sensor system. For biomedical sensing, we demonstrated our microbend fiber sensors for measurements of breathing rate/heat rate and Ballistocardiogram waveform. A new sensor for patients breathing measurement by using fiber loop ringdown spectroscopy is also introduced.

LED-camera communication system with RGB coding

A 150-km long distance sensor system is proposed by using a low-power 1480-nm laser and a 1395-nm Raman laser. As the light propagates along the transmission fiber, 1480-nm laser light is amplified by 1395-nm Raman laser through stimulated Raman scattering (SRS), and then generates amplified spontaneous emission (ASE) by pumping Erbium doped fiber (EDF). A temperature sensing distance up to 150 km is then demonstrated.

Fiber senor for long-range and biomedical measurements

Optical performance monitoring (OPM) becomes an attractive topic as the rapid growth of data rate in optical communication networks. It provides improved operation of the high capacity optical transmission systems. Among the various impairments, chromatic dispersion (CD) is one of major factors limiting the transmission distance in high-speed communication systems. Polarization-mode dispersion (PMD) also becomes a degrading effect in the system with data rate larger than 40 Gbit/s. In this paper, we summarize several CD and PMD monitoring methods based on RF spectrum analysis and delay-tap sampling. By using a narrow band fiber Bragg grating (FBG) notch filter, centered at 10 GHz away from the optical carrier, 10-GHz RF power can be used as a CD-insensitive PMD monitoring signal. By taking the 10-GHz RF power ratio of non-filtered and filtered signal, PMD-insensitive CD monitoring can be achieved. If the FBG notch filter is placed at optical carrier, the RF clock power ratio between non-filtered and filtered signal is also a PMDinsensitive CD monitoring parameter, which has larger RF power dynamic range and better measurement resolution. Both simulation and experiment results show that the proposed methods are efficient on measuring CD and PMD values in 57-Gbit/s D8PSK systems. Delay-tap sampling is another efficient method of measuring residual CD. Amplitude ratio of asynchronous delay-tap sampling plot decreases with CD monotonously, and the amplitude ratio can be obtained by using low bandwidth balanced receiver. The simulated results show that our method is efficient on residual CD measurement in 50-Gbit/s 50% RZ DQPSK systems with a 12-GHz balanced receiver. Since no modification on the transmitter or receiver is required, the proposed scheme is simple and cost effective.

150-km long distance fiber sensor system based on Raman amplification

A 100-km long distance fiber Bragg Grating (FBG) vibration sensor system is demonstrated by using a Raman pump laser source at 1395 nm and two segments of erbium doped fiber (EDF). The reflected spectrum of FBG has 30dB signal noise ratio. By using a wavelength matched FBG to achieve wavelength demodulation, vibration frequencies from 1Hz to 1000Hz has been effectively detected in this 100km long distance vibration sensor system.