Honglin Liu

Optimum design of 30-km long-distance distributed optical fiber Raman temperature sensor system

A 30km long distance distributed optical fiber Raman temperature sensor (DOFRTS) system has been made, it use new measuring temperature principle of optical fiber amplified anti-Stokes Raman spontaneous scattering. In the system, 1550nm erbium-doped optical fiber laser, a highness speed data acquisition card and signal processing technique are used. By using these technique, the problem of weak signal detection is resolved and signal to noise ratio is increased. All components of system are put into an intellectualized constant temperature box and work in constant temperature condition. Stability and environment adaptability are improved. By appraisal, performance of the system is listed as follows: length of single mode fiber: 31km, temperature rang:0-100°C (can be expanded), temperature measuring uncertainty:±2°C, temperature resolution:0.1°C, measurement time:432s, spatial resolution :3m.

Forward cascaded stimulated Brillouin scattering (SBS) in an S-band distributed G652 fiber Raman amplifier

The cascaded forward stimulated Brillouin scattering (SBS) in the S band distributed G652 fiber Raman amplifier forward pumped and backward pumped by the tunable power fiber laser and signal source is a tunable narrow spectral bandwidth(<100MHz)ECL have been studied. Forward SBS does not obey the common theory, that only weaken backward-SBS lines existed, according to conservation of energy and momentum and wave vector selected rule. Because the wave-guide character weaken the wave vector rule. The forward transmit sound wave-guide Brillouin scattering lines are generated and amplified in FRA. Forward SBS that is amplified phenomena of transmit sound wave Brillouin scattering in the FRA, during pump power is larger than the threshold value of SBS in a S band G652 FRA. The 2 orders Stokes forward Brillouin lines are present during forward pump power of FRA is 920mW, the pump power of BP line is 7.7dBm and the FRA gain is 15.05dB, the power of first order Brillouin lines is smaller than the second Brillouin scattering line. When pump power is further increased, cascaded SBS lines and comb profile are observed. The even order SBS lines is stronger than odd order SBS lines, The odd order SBS lines are named Brillouin- Rayleigh scattering lines.

Optimum design and experiment research of S-band hybrid dispersion compensation fiber Raman amplifier

Hybrid FRA is consists of distributed FRA and discrete FRA. Optimum design of S-band hybrid dispersion compensation fiber Raman amplifier has been researched by OPTIAMP DESIGN 3.3 software (made in Canada Optiwave Corporation) and gain spectrum and gain vs. power of S-band hybrid dispersion compensation fiber Raman amplifier has been researched. The backscattering spectrum of optical fiber has been measured by use 1427nm Raman laser and Q8384 optical spectrum analyzer and Stokes and anti-Stokes ZX band backscattering spectrum has been first observed and discussed, ZX band frequency shift is 1THz, band width 3THz(3dB). Pump on/off small signal gain is 23dB (pump power 700mw; G652 fiber 25.2km and DCF fiber 5.1km) and gain band width is 96nm (1440nm-1536nm). In the experiment, gain spectrum band width is wider than simulated results, practical including Stokes ZX band backscattering gain effect.

The optimization of the spatial resolution of a 30-km distributed optical fiber temperature sensor

The spatial resolution of a 30km distributed optical fiber sensor is optimized to 3m. Two methods to measure the spatial resolution of distributed optical fiber sensor were demonstrated. The lower limit of the spatial resolution of the system is determined by the width of the input laser pulse. The bandwidth of optoelectronic receiving system and the electronic system also affect the spatial resolution of the system. The bandwidth of the electronic system shall be matched with the pulse width of the laser. The spatial resolution of system can be measured directly or evaluated indirectly by the half width of the Fresnel reflection at the end of the fiber. The spatial resolution of the system reached 3m after the optimization.

Forward and backward cascaded stimulated Brillouin scattering in a S band distributed G652 fiber Raman amplifier

The forward and backward cascaded stimulated Brillouin scattering (SBS) in the backward pumped S band distributed G652 fiber Raman amplifier have been researched, pumped by the tunable power 1428nm fiber Raman laser and signal source is a tunable narrow spectral bandwidth (<100MHz)ECL. The forward SBS does not obey the common theory, that only weaken backward-SBS lines existed, according to conservation of energy and momentum and wave vector selected rule. Because the wave-guide character weaken the wave vector rule, the forward transmit sound wave-guide forward Brillouin scattering lines are generated and amplified in S band G652 FRA. Forward SBS that is amplified phenomena of transmit sound wave Brillouin scattering in the G652 FRA, during pump power is larger than the threshold value of SBS in a S band G652 FRA. Two-order SBS in the Stokes region is observed during the pump power is increased. When the FRA pump power is further increased, Cascaded SBS lines and comb profile are observed.

An experimental study on Raman spectrum of liquid-core optical fiber

The Raman spectra intensity can be enhanced in liquid core optical fiber (LCOF) .The total Raman power emitted by the LCOF is a function of the following parameters: LCOF length, LCOF loss coefficients at the laser and Raman wavelengths, the concentration of analyte and input laser power. The attenuation of the light in CS2 is small in the range from 1400nm to1700nm. We dissolved liquid CCL4 into CS2 and got different solutions of different concentrations. When the analyte concentration was changed, the analyte molecules and the numerical aperture of the LCOF were also changed, so there is an optimum concentration at which the maximum Raman spectrum can be obtained. Our experiment result is in good agreement with the calculated results. Backward Raman scattering is superior to forward Raman scattering in our experiment. Raman intensity first increases to a maximum with fiber length, then decrease because the fiber attenuation becomes dominant. Therefore, there exists the optimum fiber length. In our experiment, we find that higher Raman intensity can be obtained when the fiber length is 2m. The Raman intensity becomes powerful when the input pump power becomes larger. Raman linewidth becomes narrow when the concentration decreased. Our experiment also approves it.

Research of dispersion compensation hybrid fiber Raman amplifier in S band

Hybrid FRA consisting of general fiber G652 and dispersion compensation fiber DCF includes DCF +G652, G652 +DCF and G652+DCF +G652. The operation principle is discussed and configurations have been researched in S band. The gain and noise characteristic of 5km DCF+50km G652 fibers configuration FRA is better than 50km G652+5km DCF FRA and 25km G652+5km DCF+25km G652 FRA in experiment. The gain and noise spectrum characteristic of 5km DCF+50km G652 FRA were measured. In the DWDM fiber transmission system, the transmitted characteristic of two channels that spectral interval is 0.262nm(34.1GHz)in the dispersion compensation FRA is better than those of 50km G652 positive dispersion FRA and 5km DCF negative dispersion FRA in S band .

Phonon modes structure spectrum research in DCF optical fiber Stokes Raman scattering gain spectrum

DCF optical fiber Stokes Raman forwrad scattering and backward scattering gain spectrum have been measured by Raman laser as a pump source and high spectral resolution four grating spectrometer. There are 15 phonon modes in the Stokes forward scattering region and 18 phonon modes in the Stokes backward scattering region. In the low frequency region, there are 3 characteristic phonon modes they are 41.4 cm-1, 68.0 cm-1 and 96.7 cm-1. The characteristic Raman peaks of DCF fiber is 434.7 cm-1 and 455.4 cm-1 that are correspond to 440 cm-1 and 490 cm of normal single mode fiber as a function of pump power has been measured. Measured DCF Raman gain spectrum is different from that in common reference and books. The reasons are the high Ge02 concentration in DCF fiber and the developing of measuring technology.

Research of hybrid dispersion compensation fiber Raman amplifier

The operation principle and model of hybrid FRA is discussed. Hybrid FRA consisting of general fiber G652 and DCF includes DCT + G652, G652 + DCF and G652 + DCF + G652. The optimum design of hybrid FRA has been done by using optimum design software of FRA--OptiAmplifier 3.03. The best structure is G652 + DCF. It has many advantages: dispersion compensation of network, wide operation wavelength range (That depend on pump laser wavelength). The configuration has been set up and researched. Using Raman laser (1427nm) as an excited source, Raman gain spectrum of optical fiber and small signal amplification spectrum of is measured by optical spectrum analyzer Q8384. The hybrid FRA has gain bandwidths of 88nm in S and C band. It will increase the transmission channels of fiber communication network.

Raman effect in optical fiber and liquid-core fiber

The backscattering spectrum of optical fiber G652 (SiO2) has been researched, in the Stokes region the first order and second order Raman spectrum have been observed and the ZX band backscattering spectrum is first observed. The small signal pump on/off Raman gain spectrums have been measured by the 1427.2nm Raman laser and Q8384 optical spectrum analyzer, during different pump power. The Raman gain is 19dB and gain band width is 96nm (1440nm-1536nm) during the pump power is 700mw. The liquid-core optical fiber is made ofhollow quartz fiber filling organic liquid materials including C6H6, CS2, CCl4 and so on. The constitution and proportion of liquid materials are designed. Raman effect in liquid-core optical fiber is researched. The liquid-core optical fiber Raman amplifier are designed by using FRA optimum design software. This observed Stokes frequency shift is characteristic of the 992-cm-1, 656-cm-1, and 459cm-1 lines in C6H6 CS2, andCCl4. The Raman laser (1427mm) is used as pumping laser. A mini-ASE light source is used as signal source. The Raman spectrum has been measured by OSA Q8384 in liquid-core optical fiber. The Raman amplified bandwidth in liquid-core optical fiber is researched. The relations between the pumping threshold and liquid-core optical fiber length are attained.