Chenxia Li

Broadband near-infrared luminescence in bismuth borate glasses

We report the results of our investigation on the optical properties of the bismuth borate glass (75B2O3-25Bi2O3). Unusual near-infrared (NIR) and visible band luminescence was observed when the sample was excited by lasers working at 532 and 808 nm. The NIR fluorescent lifetime of the sample measured at room-temperature was longer than two hundred microseconds. This indicated that this glass system could be a new candidate for the broadband optical amplification and laser material covering the wavelength from 1100 to 1300 nm. The influences of preparation conditions and glass compositions on the luminescence properties of glasses were investigated. It was found that the heat-treatment under air and hydrogen atmosphere can both weaken the infrared luminescence of the materials. Furthermore, with the addition of oxidation agent CeO2, the sample did not show any NIR luminescence upon the excitation of the lasers working at 532 or 808 nm. All the results indicated that the infrared luminescence center should be Bi+ ions.

Experimental study of Raman amplification on stimulated Brillouin scattering in the G652 fibers at 1520nm

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 at 1428nm fiber Raman laser and signal source is a tunable power external cavity laser (ECL) with narrow spectral bandwidth (<100MHz). The threshold power of backward Stokes the first and second stimulated Brillouin scattering SB1- and SB2- in the backward pumped S band distributed fiber Raman amplifier is 5mW and 67.6mW, respectively. The Stokes stimulated Brillouin scattering lines is amplified by fiber Raman amplifier and fiber Brillouin amplifier. The total GA is production of the gain of Raman GR and the gain of Brillouin amplifier GB. GA=GR×GB. In experimental work, the saturation gain of SB1- and SB2- is about 50dB and 65dB respectively and the saturation gain of 25km G652 backward FRA is about 25dB, so the gain of backward fiber Brillouin amplifier SB1- and SB2- are about 25dB and 40dB, respectively. The forward SBS does not obey the common theory that only weakening backward-SBS lines existed, according to conservation of energy and momentum and wave vector selected rule. Because the wave-guide characters weaken the wave vector rule, but the forward transmit sound wave-guide forward Brillouin scattering lines are generated and amplified in S band G652 FRA. The stimulated threshold power of the forward first Stokes SBS (SB1- ) in the backward pumped FRA is 6.6mW. In experimental work, the saturation gain of SB1- is about 49dB and the saturation gain of 25km G652 backward FRA is about 10dB, so the gain of SB1- in the forward fiber Brillouin amplifier is about 39dB.

Threshold level and gain of forward stimulated Brillouin scattering in a forward pumped s-band discrete DCF fibers Raman amplifier

Amplification effect of forward stimulated Brillouin scattering (SBS) lines on the forward pumped s-band discrete DCF fiber Raman amplifier (FRA) has been studied. Pump threshold power of the forward first order Stokes SBS (FSB1-), second order Stokes SBS (FSB2-) and third order SBS (FSB3-) in the forward pumped FRA are 1.5 mW, 1.4 mW and 1.7 mW, respectively. The Stokes SBS lines are amplified by FRA and fiber Brillouin amplifier (FBA) at the same time. Gain of amplification is given as GA=GR · GB, where GR is Raman gain and GB is Brillouin gain. Saturation gain of FSB1-, FSB2- and FSB3- are about 52 dB, 65 dB and 65 dB, respectively. The saturation Raman gain of 10 km DCF forward FRA is about 14 dB, so Brillouin gain of FSB1-, FSB2- and FSB3- are about 38 dB, 51 dB and 51 dB, respectively. The forward cascaded SBS lines have been observed.

Recent progress in distributed optical fiber raman sensors

A brief review of recent progress in researches, productions and applications of distributed fiber Raman sensors at China Jiliang University (CJLU) is presented. In order to improve the measurement distance, the accuracy, the space resolution, the ability of multi-parameter measurements, and the intelligence of distributed fiber sensor systems, a new generation fiber sensor technology based on the optical fiber nonlinear scattering fusion principle is proposed. A series of new generation distributed fiber sensors are investigated and designed, which consist of new generation ultra-long distributed fiber Raman and Rayleigh scattering sensors integrated with a fiber Raman amplifier (FRA), auto-correction full distributed fiber Raman temperature sensors based on Raman correlation dual sources, distributed fiber Raman temperature sensors based on a pulse coding source, distributed fiber Raman temperature sensors using a fiber Raman wavelength shifter, a new type of Brillouin optical time domain analyzers (BOTDA) integrated with a fiber Raman amplifier, distributed fiber Raman and Brillouin sensors integrated with a fiber Raman amplifier, and distributed fiber Brillouin sensors integrated with a fiber Brillouin frequency shifter. Sensor networks are important components of the internet of things. The distributed optical fiber sensor network (Rayleigh, Raman, and Brillouin scattering) is a 3S (smart materials, smart structure, and smart skill) system, which is easy to construct smart fiber sensor networks. The distributed optical fiber sensor has been applied to the power grids, railways, bridges, tunnels, roads, constructions, water supply systems, dams, oil and gas pipelines and other facilities, and can be integrated with wireless networks.

Study and manufacture of gain flattened S-band distributed dispersion compensation fiber Raman amplifier

Now the communication band of fiber focuses on C-band, but with increasing demand of fiber communication capacity, the communication band will extend to the S-band and L-band and fiber Raman amplifier will play a very important role in this process. In this paper, actual fiber Raman gain spectrum using single high power fiber Raman laser as pump was tested and the proper chirped Bragg fiber grating as gain flattening filter was designed to flatten actually tested gain spectrum. Besides, FWDM (film wavelength division multiplexer) is used as the multiplexer of signals and 1427nm/1505nm CWDM (coarse wavelength division multiplexer) is used as pump-signal coupler. The gain media are 50 km G652 fiber and 5km DCF (dispersion compensation fiber). The gain is 10dB of S-band fiber dispersion compensation Raman amplifier from1487.88nm~1541.88nm (total 53nm bandwidth) with gain ripple ± 0.6dB was successfully obtained. Besides, the effect caused by different location ways of different type fibers was also discussed. It is very significant for extending range of communication band of fiber and increasing the capacity of fiber communication especially for ultra-long haul and ultra-high capacity communication system.

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.

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.