Optimum index profile of the perfluorinated polymer-based GIpolymer optical fiber and its dispersion properties

The significant advantages in bandwidth and low material dispersion of perfluorinated (PF) polymer-based graded-index polymer optical fiber (GI POF) are theoretically and experimentally reported for the first time. It is confirmed that the low attenuation and low material dispersion of the PF polymer enables 1 Gb/s km and 10 Gb/s km transmission at 0.85-μm and 1.3-μm wavelengths, respectively. The PF polymer-based CI POF has very low material dispersion (0.0055 ns/nm·km at 0.85 μm), compared with those of the conventional PMMA-based POF and of multimode silica fiber (0.0084 ns/nm km at 0.85 μm). Since the PF polymer-based GI POF has low attenuation from the visible to near infrared region, not only the 0.65-μm wavelength which is in the low attenuation window of the PMMA-based GI POF, but other wavelengths such as 0.85-μm or 1.3-μm etc. can be adopted for the transmission wavelength. It is clarified in this paper that the wavelength dependence of the optimum index profile shape of the PF polymer-based GI POF is very small, compared to the optimum index profile shape of the silica-based multimode fiber. As a result, the PF polymer-based GI POF has greater tolerance in index profile variation for higher speed transmission than multimode silica fiber. The impulse response function of the PF polymer-based GI POF was accurately analyzed from the measured refractive index profile using a Wentzel, Kramers, Brillouin (WKB) numerical computation method. By considering all dispersion factors involving the profile dispersion, predicted bandwidth characteristic of the PF polymer-based GI POF agreed well with that experimentally measured     

Temperature dependence of signal gain in Er3+-dopedoptical fiber amplifiers

Temperature-dependent signal gain characteristics at signal wavelengths of 1.536 and 1.552 μm in Er³⁺-doped optical fibers with a temperature range of -40 to 80°C are reported for 0.98 and 1.48 μm pumping. The temperature dependences of signal gain strongly depend on fiber length, pump wavelength, and signal wavelength. The fiber length at which signal gain temperature insensitivity occurs is found for the amplification of a 0.98-μm-pump-1.536-μm-signal, a 0.98-μm-pump-1.552-μm-signal, and a 1.48-μm-pump-1.536-μm-signal. It is confirmed theoretically that the temperature dependences result from linear changes in the fluorescence, and absorption cross sections at the signal and pump wavelengths, and a shift in the effective pump wavelength     

An optical fiber amplifier for wide-band wavelength range around1.65 μm

The optical amplification characteristics of a 0.781-μm pumped thulium-doped fiber in the wavelength range of 1.6-1.7 μm are discussed. A maximum net gain of 2.0 dB was obtained for 1.69-μm operation. This optical fiber amplifier is suitable for in-service monitoring and identifying fibers operating at 1.2-1.6 μm     

Far-field radiation and modal dispersion of 1310 nmdispersion-optimized fiber at 850 nm

Far-field radiation pattern measurements have been used to evaluate the modal structure and dispersion associated with 0.85-μm wavelength light launched from high-brightness light-emitting diodes into TIA class-IVa fiber. The measured far-field radiation pattern of the light intensity emitted from the end of the optical fiber is compared to the far-field radiation pattern calculated from the Fraunhofer approximation to the diffraction integral with the result that two linearly polarized modes propagate in the optical fiber and the optical power is nearly equally distributed between the two modes. The modal dispersion associated with the use of a 0.85-μm wavelength emitter and a TIA class-IVa fiber is evaluated to be 2.3 ns/km, which is adequate for a variety of local-area networks and point-to-point optical communication links     

Optical full-duplex transmission with diode laser amplifiers

Error-free, simultaneous bidirectional optical transmission at 50 Mb/s over 5.5 km of fiber using only a single antireflection coated Fabry-Perot laser transmitter/detector at each end is demonstrated. A baseband digital signal is transmitted in one direction, while a digitally modulated subcarrier signal is transmitted in the opposite direction. At the 1.5-μm operating wavelength, the system length is dispersion limited due to the wide spectral widths of the signals. Therefore, it is expected that a system operating at the 1.3-μm low-dispersion window will show an improved capacity. The additional device capability of optical gain makes this scheme attractive in multiport-full-duplex applications     

A widely tunable narrow linewidth semiconductor fiber ring laser

We have demonstrated a novel approach to obtain a 0.1-nm line width laser with 38-dB sidemode suppression by utilizing a 1.3-μm semiconductor optical amplifier in a fiber unidirectional ring that consists of a linear polarizer and polarization controllers. The laser has a low-threshold current of 22.5 mA as well as a wide tuning range of 28 nm. The new approach is applicable to the 1.55-μm region as well. It is expected that nanosecond wavelength tuning speed is feasible using this approach in conjunction with fast electrooptic polarization controllers, short cavities and low-cavity losses     

非制冷型中长波铟砷锑探测器

工作在中、长波红外波段(波长5~12μm)的红外探测器在红外制导、红外成像、环境监测及资源探测等方面有着重要而广阔的应用前景。目前中国军用和民用对这一波段的非制冷型、快速响应的光子型红外探测器有迫切需求。文中用熔体外延(ME)法在InAs(砷化铟)衬底上生长的InAs0.05Sb0.95(铟砷锑)厚膜单晶,制作了高灵敏度、非制冷型、中长波光导型探测器,探测器上安装了Ge(锗)浸没透镜。傅里叶变换红外(FTIR)吸收光谱显示InAsSb材料的本征吸收边出现在波长8μm以后。InAs0.05Sb0.95探测器的光谱响应波长范围为2~9μm。室温下,在波长6.5μm处的峰值探测率Dλp*达到5.4×109 cm·Hz1/2·W-1,在波长8.0μm和9.0μm处的探测率D*分别为9.3×108和1.3×108 cm·Hz1/2·W-1,显示了InAsSb探测器的优越性能及对红外探测和成像的应用前景。     

Gain-shifted dual-wavelength-pumped thulium-doped fiber amplifierfor WDM signals in the 1.48-1.51-μm wavelength region

We constructed a gain-shifted dual-wavelength-pumped (1.05/1.56 μm) thulium doped fiber amplifier (TDFA) for wavelength-division-multiplexing (WDM) signals in the 1.48-1.51-μm, wavelength region. We obtained a gain of larger than 20 dB and a noise figure of less than 7 dB in the range from 1478 to 1505 nm. Amplifier saturated output power was +20.1 dBm with an optical-to-optical conversion efficiency of 9.1% for 12-channel WDM signals. We also obtained a successful bit error rate performance for signals modulated at 10 Gb/s when the gain-shifted TDFA was used in an optical preamplifier configuration. These results confirm the feasibility of using the gain-shifted TDFA as both a booster and an optical preamplifier in WDM networks     

An efficient low voltage, high frequency silicon CMOS lightemitting device and electro-optical interface

A silicon light emitting device was designed and realized utilizing a standard 2-μm industrial CMOS technology design and processing procedure. The device and its associated driving circuitry were integrated in a CMOS integrated circuit and can interface with a multimode optical fiber. The device delivers 8 nW of optical power (450-850 nm wavelength) per 20-μm diameter of chip area at 4.0 V and 5 mA. The device emits light by means of a surface assisted Zener breakdown process that occurs laterally between concentrically arranged highly doped n⁺ rings and a p⁺ centroid, which are all coplanarly arranged with an optically transparent Si-SiO₂ interface. Theoretical and experimental determinations with capacitances and series resistances indicate that the device has an intrinsic high-frequency operating capability into the near gigahertz range     

1.5-μm-band optical time domain reflectometer for single-modeoptical fiber using a P2O5-highly-doped fiberRaman laser

A wide-dynamic-range 1.5-μm-band optical time-domain reflectometer (OTDR) for single-mode optical fibers using a P₂O₅-highly-doped fiber Raman laser light source and a cooled Ge-p-i-n photodiode is realized for the first time. The stimulated-Raman-scattering properties of P₂O₅-doped single-mode fiber are investigated. Using this fiber and an Nd:YAG laser operating at 1.32 μm, a high-power light pulse at 1.59 μm is generated with high efficiency. Using the stimulated-Raman-scattering light as the light source and a high-sensitivity optical receiver, a 1.5-μm-band OTDR having a one-way dynamic range of 35 dB is realized     

单偏振单模微结构聚合物光纤的设计

设计了一种聚甲基丙烯酸甲酯(PMMA)基的单偏振单模(SPSM)微结构聚合物光纤(MPOF)。采用全矢量平面波展开法并结合完美匹配边界条件,对其偏振特性进行了理论模拟。详细讨论了微结构光纤参数的变化对单偏振单模带宽和工作波长的影响,发现在0.57～0.71μm的可见光波长范围,由于基模两个正交偏振模的截止波长不同,这种微结构聚合物光纤只能传输基模中的一个偏振模。光束传播法计算表明,在波长0.65μm处具有7圈空气孔的单偏振单模微结构聚合物光纤的传导偏振模约束损耗仅为1.24dB/m,这种低损耗的单偏振单模微结构聚合物光纤可有效消除传统保偏光纤固有的偏振串扰和偏振模色散。     

Tunable wavelength filter using nano-sized droplets of liquidcrystal

An electrically tunable optical filter has been developed that uses a polymer containing fine droplets of nematic liquid crystal as the active cavity in a Fabry-Perot interferometer (FPI). This FPI filter, whose finesse was 62, had a free spectral range of 37 nm in the 1.55-μm range with a full-width at half maximum of 0.6 nm and a transmission loss of 2.4 dB. The polarization dependent loss was smaller than 0.17 dB. The transmitted peak wavelength decreased with an electric field. This resulted in a tuning range of 10 nm at 300 V. The switching time was about 370 μs     

Linear InGaAsP edge-emitting LED's for single-mode fibercommunications

A 1.3-μm edge-emitting diode with a linear radiance and high coupled power into a fiber is described. The LED yields 60 μW of coupled power into a single-mode fiber at a driving current of 100 mA and an ambient temperature of 25°C. A V-groove structure with an optical absorption region separated from an active region is used. At active layer thicknesses below 0.14 μm, linear current-light output characteristics are obtained. The spectral modulation depth is 0% over the entire emission spectral width of 75 nm, and coherence length is 22.5 μm. LED characteristics are achieved in the range from -30 to 85°C at a driving current of 100 mA. The LEDs exhibit a cutoff frequency of 250 MHz. LED reliability is discussed using results of accelerated aging carried out at the ambient temperatures of 50, 125, and 200°C. The activation energy of degradation is determined to be 0.63 eV, and LED half-lives are estimated to be in excess of 10⁶ h     

Tunable wavelength filter using a Bragg grating fiber thinned byplasma etching

We studied a tunable wavelength filter using a single-mode fiber Bragg grating with a cladding thinned by reactive plasma etching. Reflection wavelength shifts were demonstrated by controlling the effective refractive index or the period of the grating. When liquid paraffin was used for additional cladding on a thinned grating fiber of 19-μm diameter, the shift rate of 0.055 nm/°C was obtained. In the case of applying the tension to the grating region, the shift rate was 3.4 nm/100 V for the fiber of 41-μm diameter     

Analysis of the response of long period fiber gratings to externalindex of refraction

This paper demonstrates that the change in wavelength of a long period fiber grating attenuation band with changes in external index of refraction can be enhanced by proper selection of the grating period. We calculate and experimentally verify that the wavelength shift caused by changing the external index from n=1 to n=1.44 of the attenuation band which appears in the 1400-1600 nm region in a 200-μm period grating is four times that in a 350-μm period grating. Changes in the spectrum over a wavelength range from 1100 to 1600 nm and 1相似文献   

Compensation of dispersion in optical fibers for the 1.3-1.6 μmregion with a grating and telescope

The transmission of ultrashort optical pulses over long distances in optical fibers is limited by pulse broadening due to group velocity dispersion. A grating and telescope dispersion compensator with group velocity dispersion of equal magnitude and opposite sign can compensate for the fiber dispersion. The possible benefits of such dispersion compensation in the 1.3-1.6-μm wavelength region are investigated. The results show that compensation of first-order dispersion at 1.55 μm in a fiber with zero dispersion near 1.3 μm is primarily limited by the second-order dispersion of the grating and the telescope compensator. For a wavelength slightly greater than the zero dispersion wavelength, both the first- and second-order group velocity dispersion can be canceled by the grating and telescope dispersion compensator, allowing transmission exceeding 100 Gb/s over 100 km     

Broad-band mid-span spectral inversion without wavelength shift of1.7-ps optical pulses using a highly nonlinear fiber Sagnacinterferometer

We demonstrate broad-band mid-span spectral inversion without wavelength shift of short optical pulses using a highly nonlinear fiber Sagnac interferometer. The 1.55-μm optical pulses with a 1.7-ps pulsewidth are transmitted over 40 km of standard fiber, showing the suitability of this technique for broad-bandwidth second-order dispersion compensation in high-bit-rate optical fiber transmission systems     

空间用宽截止长波红外带通滤光片的设计与镀制

针对空间用宽截止长波红外带通滤光片具有通带内平均透射率高、抑制带截止深度深、波纹系数小,可适应复杂环境条件、具有高稳定性和高可靠性等特点,论述了宽截止长波红外带通滤光片的设计原则和方法.采用"会聚光红外光学系统"和等离子体辅助沉积工艺成功镀制了空间用宽截止长波红外带通滤光片.指出等离子体辅助沉积工艺更有利于长波红外滤光片膜层的显微结构改善和残余应力的消除.     

Transmission loss of a 125-μm diameter PANDA fiber with circularstress-applying parts

The transmission loss of a 125-μm diameter polarization-maintaining and absorption-reducing optical fiber (the PANDA fiber) with circular stress-applying parts (SAPs) has been investigated. The loss is calculated at a 1.55- μm wavelength for SAPs consisting of B₂O₃ doped silica glasses. The experimental measurements show the validity of the analysis. It is shown that, when the half distance between SAPs is more than 2.2 times the core radius, the additional transmission loss due to B₂O₃ absorption is less than 0.05 dB/km with normalized frequency of 2.2 to 2.4 and a B₂O₃ dopant concentration of 20 mol.%. As a result, it has been confirmed that transmission losses of 125-μm diameter PANDA fibers can be comparable to those of commercially available single-mode optical fibers     

Devitrification in annealed optical fiber

The decrease in transmittance of annealed optical fiber has been measured versus temperature and time. The annealing loss is due to the devitrification of the glass and OH absorption in the 1200 to 1500 nm wavelength region. Both loss mechanisms propagate primarily from the surface into the core. However, to increase the OH absorption significantly, annealing times greater than 10 h are required. Fibers heated from 1000 to 1300°C in an air atmosphere quickly devitrify and their transmittance approaches zero. Also, the current sensitivity of annealed fiber current sensors versus annealing time at 850°C has been measured. A decrease in the current sensitivity is attributed to devitrification in the fiber