Pump-induced refractive index modulation and dispersions inEr3+-doped fibers

A novel measurement system provides determination of pump induced phase shifts in erbium doped fibers with an accuracy of ~π/20. Using this system, a systematical analysis of the pump induced modulation of the refractive index and dispersions for a signal at 1550 nm and a pump at 980 nm is reported. The analysis contains measurements of pump induced refractive index changes as function of wavelength, pump power, and doping concentration. A model taking account of the contribution to the refractive index changes from optical transitions between ⁴ I_15/2 states and ⁴I_13/2 states in Er³⁺ yields good agreement to experimental results apart from a wavelength independent offset. The offset is interpreted to originate from high energetic optical transitions. The results show that for a large refractive index modulation, a short and highly doped fiber should be used with limited amplified spontaneous emission effect. In optical communication systems comprising erbium doped fiber amplifiers, a tradeoff between dispersion and amplification must be made     

S-C-L triple-band double-pass erbium-doped silica fiber amplifier with an embedded DCF module for CWDM applications

In this paper, the authors present a double-pass triple-band doped fiber amplifier including an embedded dispersion-compensating fiber. The amplifier employs only silica-based erbium-doped fibers to achieve signal amplification over S-, C-, and L-bands. Experimental characterization is carried out in terms gain and noise figure over the coarse-wavelength-division-multiplexing (CWDM) wavelength grid. By providing optical gain to seven CWDM channels spectrally located between 1490 and 1610 nm, the amplifier can extend the reach of a CWDM optical bus well beyond the 100-km limit.     

Collagen network as the scaffold for spontaneously distributed optical resonators

The idea behind this work was to acquire one dimensional lasing in the Rhodamine 6G dye doped collagen fibers with the control of random lasing phenomenon properties by changing the dye molecular arrangement. We show that a simple manipulation of the dye concentration in biopolymeric fibril matrix bulk and an additional use of α-cyclodextrin (α-CD) molecules determine formation of specific dye aggregates and as a consequence the shift of the random lasing emission wavelength in the desired direction. The analysis of the light transport mean free path in function of the dye and (α-CD) concentration was done with the use of coherent back scattering technique.     

Wideband Hybrid Fiber Amplifier Using Er‐Doped Fiber and Raman Medium

In this paper, we report the experimental results of a hybrid wideband fiber amplifier. The amplifying medium is a concatenated hybrid fiber consisting of Er‐doped fiber (EDF) and dispersion compensating fiber (DCF). The gain mechanisms are based on stimulated emission in the EDF and stimulated Raman scattering (SRS) in the DCF. Since we simultaneously use optical amplification by the two processes, the gain bandwidth is easily expanded over 105 nm by a two‐tone pumping scheme. Using an experimental setup constructed with a hybrid structure of EDF‐DCF‐EDF, we analyzed the spectral behavior of amplified spontaneous emission for pumping powers. We achieved an optical gain of over 20 dB in the wavelength range from 1,500 to 1,600 nm under optimized pumping conditions to make the spectral gain shape flat.     

Design of Hybrid Optical Amplifiers for High Capacity Optical Transmission

This paper describes our design of a hybrid amplifier composed of a distributed Raman amplifier and erbium‐doped fiber amplifiers for C‐ and L‐bands. We characterize the distributed Raman amplifier by numerical simulation based on the experimentally measured Raman gain coefficient of an ordinary single mode fiber transmission line. In single channel amplification, the crosstalk caused by double Rayleigh scattering was independent of signal input power and simply given as a function of the Raman gain. The double Rayleigh scattering induced power penalty was less than 0.1 dB after 1000 km if the on‐off Raman gain was below 21 dB. For multiple channel amplification, using commercially available pump laser diodes and fiber components, we determined and optimized the conditions of three‐wavelength Raman pumping for an amplification bandwidth of 32 nm for C‐band and 34 nm for L‐band. After analyzing the conventional erbium‐doped fiber amplifier analysis in C‐band, we estimated the performance of the hybrid amplifier for long haul optical transmission. Compared with erbium‐doped fiber amplifiers, the optical signal‐to‐noise ratio was calculated to be higher by more than 3 dB in the optical link using the designed hybrid amplifier.     

Fluorescence and superfluorescence line narrowing and tunability ofNd3+ doped fibers

The inhomogeneous behavior of the 1.06 μm-neodymium transitions in doped optical fibers have been investigated, using the fluorescence line narrowing technique, pumping on the ⁴F_3/2 and ⁴F_5/2 sublevels at 4 K. Each observed transition has been identified. As the pump wavelength varies, the shift of the main fluorescence line is 40 nm, with the two pumping levels. We have studied the spectral behavior of the superfluorescence as a function of the pump wavelength, the temperature, and the absorbed power. The spectral evolution depends on λ_p with 19 nm-tuning range at low temperature. At 300 K, the quasihomogeneous behavior of the transition decreases the tunability to 14 nm. Based on these results, we present a simple technique permitting precise prediction of gain and spectral line shapes of superfluorescent Nd-doped fiber sources     

Simultaneous Amplification at Two Wavelengths Near 1300 nm in a 6.5-cm-Long Bismuth-Doped Silica Glass

We demonstrated the simultaneous optical amplification at two wavelengths near second telecommunication windows in a 6.5-cm-long bismuth-doped silica glass with 810-nm excitation. Optical amplification at a single wavelength in$O$-band (1260–1360 nm) is also reported in this letter. This technique can be used for wavelength-division-multiplexing optical amplifiers at 1300 nm, which is the range of zero-dispersion for silica fibers.     

Precision fabrication of D-shaped single-mode optical fibers by insitu monitoring

A technique has been developed to locally remove, over a distance of several millimeters of fiber length, the cladding layer of single-mode (at the 1300 nm wavelength) optical fibers with 1 μm depth precision by use of mechanical lapping and in situ optical transmission monitoring. A cylinder lap dressed with diamond is used to perform high-pressure mechanical lapping. The in situ monitoring technique is based on the specific different attenuations exhibited by higher order propagating modes (for 633 nm light) as the cylinder penetrates into the fiber. Advantages include relatively rapid overall processing, high lapping rate, good optical surface quality, and 1 μm precision. Experimental results are presented and analyzed by an approximate geometrical-optics model     

偶氮染料掺杂高分子薄膜的光学常数

在单晶硅片上 ,以旋涂 (Spin- Coating)法制备了推 -拉型偶氮染料掺杂高分子 (PMMA)薄膜 ,其中二甲基胺基 [N(CH3 ) 2 ]作为推电子基团 ,羧基 (COOH)作为拉电子基团。利用椭圆偏振光谱和吸收光谱 ,研究了薄膜的复折射率、复介电函数和吸收系数 ,分析了影响薄膜电子光谱的因素。结果表明 ,该薄膜在 40 0～ 60 0 nm波长范围内 ,存在强而宽的吸收 ,并发现染料分子的聚集状态对其吸收光谱有较大的影响