Reduced temperature sensitivity of lasing wavelength in near-1.3 /spl mu/ InAs/GaAs quantum-dot laser with stepped composition strain-reducing layer

An InGaAs strain-reducing capping layer with a stepped composition is shown to significantly reduce the temperature sensitivity of the lasing wavelength in a 1.3 mum InAs/GaAs quantum-dot laser. With this technique, the sensitivity is reduced from 0.48 nm/K for a laser with standard capping layer to 0.11 nm/K for the new design over the temperature range 20-130degC     

The first hot pluggable 2.5 Gb/s DWDM transceiver in an SFP form factor

For the first time, a hot pluggable 2.5 Gb/s DWDM transceiver with 100 GHz spacing in an SFP form factor has been presented. We demonstrate transmit wavelength drift of plusmn9 pm and optical output power stability of 0.2 dB over an operating case temperature range of -5degC to 70 degC. The minimum receive sensitivity was -33.2 dBm for back-to-back, -32.6 dBm after transmission over 80 km of standard SMF, and -28 dBm for an OSNR level of 16 dB at a BER of 1 times 10^-10      

High-Performance Directly Modulated 1.3- μm Undoped InAs–InGaAs Quantum-Dot Lasers

In this letter, we report on experimental results of directly modulated single-transverse mode 1.3-mum InAs-InGaAs quantum-dot (QD) lasers in a wide temperature range. A 3.125-Gb/s data modulation over temperature with an extinction ratio up to 10 dB is reported. Moreover, 10-Gb/s eye patterns at 15 degC and 50 degC and 5-Gb/s modulation in the whole explored temperature range (15 degC-85 degC) are demonstrated. These results were obtained by exploiting heterostructures containing six layers of high modal gain InAs QDs grown without incorporation of p-doping in the active region or tunnelling injection structure implementation. QD lasers exhibited a saturation modal gain as high as 36.3 cm^-1, ground state lasing from short cavities down to 400-mum length and a characteristic temperature of about 110 K in a large temperature range between 15 degC and 85 degC     

Environmentally Stable Fabry–PÉrot-Type Strain Sensor Based On Hollow-Core Photonic Bandgap Fiber

We design and demonstrate a miniature all-fiber Fabry-Perot (F-P) interferometric sensor based on hollow-core photonic bandgap fiber where the strain is gauged by measuring the spectrum shift of the reflected optical signal. The F-P cavity in the order of millimeters is fabricated by simple techniques of cleaving and fusion splicing. The sensitivity of the sensor is 1.55 pm/muepsiv at the wavelength of 1550 nm and the contrast of the intensity reaches 4-6 dB. Temperature and bend insensitivity and excellent repeatability of the sensor make it convenient for a wide range of applications.     

High-Sensitivity Measurement of Thermal Deformation in a Stacked Multichip Package

The thermal deformation of a stacked multichip package, which is a newly developed electronic package, was measured by phase-shifting moireacute interferometry. We developed this method using a wedged glass plate as a phase shifter to obtain displacement fields having a sensitivity of 30nm/line. This method also enabled the quantitative determination of the strain distributions in all observation areas. Thermal loading was applied from room temperature (25degC) to elevated temperatures of 75degC and 100degC where the thermal strains were examined and compared. The results showed that the longitudinal strain epsiv_xx was concentrated at the ends of two silicon chips, and the longitudinal strain epsiv_yy increased between the two silicon chips. The shear strain gamma_xy increased at the end of the lower silicon chip from 0.17% to 0.30% when the temperature increased by 25degC     

Ultra-long-distance fbg sensor system based on spectrum-limited fourier domain modelocking fibre laser with raman pumps

A novel ultra-long-distance (up to 76 km) fibre Bragg grating (FBG) sensor system based on a spectrum-limited Fourier domain modelocking fibre laser is proposed. Raman pumps are employed to form a Raman amplifier to compensate the transmission loss of the long fibre and ensure ultra-long-distance sensing. Strain sensing based on such an ultra-long-distance FBG sensor system is demonstrated with a signal-to-noise ratio over 22 dB and a sensitivity of 1.03 pm/muepsiv in the wavelength domain or 18.3 ns/muepsiv in the time domain.     

Strain and temperature characterisation of sensing head based on suspended-core fibre in Sagnac interferometer

The study of the strain and temperature characteristics of a sensing head based on a four-hole suspended-core fibre in a Sagnac interferometric configuration is reported. It is shown that, for the case of using an uncoated suspended-core fibre, a relatively large strain sensitivity is obtained (/spl simeq/1.94 pm/μ/spl varepsilon/), while the temperature sensitivity is small (/spl simeq/0.29 pm/°C), pointing to a temperature-independent strain sensor. When the fibre is coated, the strain sensitivity remains essentially the same, while the temperature sensitivity becomes much larger and with a value that changes with the localisation of the temperature variation range.     

Wide Temperature Range Operation of a 1.55-$mu$m 40-Gb/s Electroabsorption Modulator Integrated DFB Laser for Very Short-Reach Applications

We present the uncooled operation of a 1.55- mum 40-Gb/s InGaAlAs electroabsorption modulator (EAM) integrated distributed-feedback (DFB) laser within a temperature range of 95degC (-15degC to 80degC ). To the best of our knowledge, this is the largest temperature range reported so far for such a 40-Gb/s EAM integrated DFB laser. We designed the EAM to operate at high speed by reducing the electrical parasitics, and we achieved a 3-dB frequency bandwidth of over 39 GHz for an EAM length of less than 150 mum. We demonstrated a 2-km single-mode fiber (SMF) transmission at 40-Gb/s over a wide temperature range of -15degC to 80degC by adjusting only the bias voltage to the EAM while keeping the modulation voltage swing constant at 2.0 V when the temperature changed. We achieved a dynamic extinction ratio of over 8.2 dB and a 2-km SMF transmission with a power penalty of less than 2 dB over a wide temperature range.     

A Fiber Ring Laser Dilatometer for Measuring Thermal Expansion Coefficient of Ultralow Expansion Material

A new type of measuring system for coefficient of linear thermal expansion (CTE) of ultralow expansion (ULE) material by using a fiber ring laser is introduced in this letter. The lasing frequency of the laser is stabilized to one of the transmission peaks of the etalon filter by controlling the resonant frequency of the tunable filter. The spacer of the (Fabry-Perot type) etalon filter is made of ULE material. We could measure the CTE of ULE by measuring the optical frequency change caused by the temperature change of the etalon spacer. The combined standard uncertainty is estimated as the value of plusmn36.6 ppb/degC in the temperature range from 5degC to 60degC.     

10-Gb/s Direct Modulation up to 100 $^{circ}$C Using 1.3- $mu$m-Range Metamorphically Grown Strain Compensated InGaAs–GaAs MQW Laser on GaAs Substrate

We have realized 10-Gb/s direct modulation up to 100degC using a metamorphic InGaAs multiple-qunatum well (MQW) laser on a GaAs substrate. The highly strained InGaAs quantum well (QW) and strain-compensated GaAs barrier layer allowed 1.3-mum-range lasing and an increased number of QWs (six). This laser with a 200-mum-long short cavity and a narrow ridge had maximum relaxation oscillation frequencies of 13 and 6 GHz at 25degC and 100degC, respectively. A 10-km single-mode fiber error-free transmission was successfully obtained at a temperature of 85degC .     

Strain sensor without temperature compensation based on LPFG with strongly rotary refractive index modulation

The strain and temperature characteristics of a novel long-period fibre grating with strongly rotary refractive index change modulation (S-R-LPFG) was investigated, this believed to be for the first time. It was observed that the two split resonant peaks continually separated when the strain was applied to it, and the temperature sensitivities are all 0.07 nm/degC. Such kinds of S-R-LPFG can be used to measure strain by using the wavelength difference between the two split peaks, which do not need temperature compensation because the two peaks shift to the same direction and have the same temperature sensitivity when environmental temperature changes.     

Reduced Temperature Dependence of Lasing Wavelength in Membrane Buried Heterostructure DFB Lasers With Polymer Cladding Layers

An athermal operation of the lasing wavelength in a membrane buried heterostructure distributed feedback (BH-DFB) laser was demonstrated by adopting a polymer (benzocyclobutene) cladding layer which has a negative temperature coefficient of refractive index. Membrane BH-DFB lasers of core thickness 65 nm were operated under room-temperature continuous-wave conditions. The temperature dependence of the lasing wavelength was measured to be 2.45times10^-2 nm/degC, which is about 20%-30% of that for conventional semiconductor lasers     

All-optical flip-flop based on coupled laser diodes

An all-optical set-reset flip-flop is presented that is based on two coupled lasers with separate cavities and lasing at different wavelengths. The lasers are coupled so that lasing in one of the lasers quenches lasing in the other laser. The flip-flop state is determined by the laser that is currently lasing. A rate-equation based model for the flip-flop is developed and used to obtain steady-state characteristics. Important properties of the system, such as the minimum coupling between lasers and the optical power required for switching, are derived from the model. These properties are primarily dependent on the laser mirror reflectivity, the inter-laser coupling, and the power emitted from one of the component lasers, affording the designer great control over the flip-flop properties. The flip-flop is experimentally demonstrated with two lasers constructed from identical semiconductor optical amplifiers (SOAs) and fiber Bragg gratings of different wavelengths. Good agreement between the theory and experiment is obtained. Furthermore, switching over a wide range of input wavelengths is shown; however, increased switching power is required for wavelengths far from the SOA gain peak     

Studies on strain and temperature characteristics of a slanted multimode fiber Bragg grating and its application in multiwavelength fiber Raman ring laser

Detailed strain and temperature characteristics of a 2/spl deg/ slanted multimode fiber Bragg grating (MFBG) are developed theoretically and observed experimentally. Results show that the strain and temperature sensitivities are almost the same for different transmission dips of the 2/spl deg/ slanted MFBG. Utilizing two characteristics of the 2/spl deg/ slanted MFBG, namely 1) resonant wavelength intensities strongly affected by excited mode propagating before the grating and 2) uniform strain sensitivities of different resonant wavelengths, a switchable and tunable multiwavelength fiber Raman ring laser is realized. The configuration is simple and multipurpose. Results show that the laser can generate single-, dual-, three-, four-, and five-wavelength lasing by switching between each operation if a mode scrambler (MS) that is inserted in front of the slanted MFBG is adjusted; furthermore, a 4.2-nm continuous wavelength-tuning range is achieved by straining the slanted MFBG when the MS is fixed.     

CO2激光刻写长周期光纤光栅与光纤MZ结构的双参数传感特性

为了实现温度与应变的双参数高精度传感测量,提出了一种CO2激光刻写长周期光纤光栅（Long Period Fiber Grating,LPFG）与光纤马赫-增德尔（MZ）干涉型结构的光纤传感器,利用CO2激光刻写制作LPFG并利用错位熔接法制备光纤MZ结构,将二者级联并实时监测温度及应变变化时的透射谱变化,研究了其传感原理并验证了其温度及应变传感特性。实验结果表明:该双参数光纤传感器的LPFG仅对温度敏感,MZ干涉结构对温度和应变都敏感;在温度范围35~70℃时,LPFG特征波长升温灵敏度38.57 pm/℃,降温灵敏度39.17 pm/℃;MZ干涉结构特征波长升温灵敏度38.57 pm/℃,降温灵敏度为37.50 pm/℃;当应变范围0~450 时,MZ干涉结构加载灵敏度4.01 pm/,卸载灵敏度为4.24 pm/。为温度和应变的实时测量提供了一种灵敏度高、线性度好的光纤传感器。     

Narrow Tunable Polysilane Optical Waveguide Bragg Grating Filters

A new Bragg grating filter (BGF) in a polysilane waveguide has been fabricated by a two-beam interferometric photobleaching method using a He-Cd laser. A narrow reflected bandwidth of 0.4 nm was measured using a 1.55-mum light-emitting diode. The temperature dependence of the BGF was measured as 0.096 nm/degC with temperature control over a range between 30 degC and 70 degC and exhibited a good coincidence with the theoretical values     

A temperature-stable semiconductor laser based on coupled waveguides

The design of a stripe semiconductor laser with a composite waveguide formed of two tunneling-coupled waveguides, one of which is narrow and contains the active medium and the other of which is wide and forms the optical mode is considered. It is shown that temperature stabilization of the lasing wavelength can be attained with such a semiconductor laser design. Stabilization of the wavelength can be brought about by lasing in antiresonance conditions of coupling of two waveguides; these conditions arise in a narrow range of wavelengths that depends on temperature only slightly. Calculations performed at the parameters characteristic of the InAlGaAsP laser system show that it is possible to reduce the temperature dependence of the lasing wavelength by a factor of 3 in the temperature range with the width of 60 K.     

A Taper-Fused Microspherical Laser Source

We report on the realization of an integrated lasing device consisting of a microsphere optical resonator fused to a tapered optical fiber. A microsphere fabricated from Er: Yb-codoped phosphate glass is heated above its glass transition temperature of 375degC by pumping it at 977 nm with 70 mW via a tapered optical fiber. The onset of thermal stress in the glass at a maximum pumping power results in the sphere melting and fusing to the taper coupler, without inhibition of whispering gallery mode lasing. A taper-fused microsphere laser with ~4.5 muW of lasing power at 1593 nm is demonstrated.     

Wavelength selection and tuning by optical control in a two-segmenterbium-doped fiber laser

A new method for controlling the wavelength of an Er³⁺-doped fiber laser is proposed and demonstrated. Using two sections of dissimilar Er³⁺-doped fiber and pumping them separately, switching among several distinct lasing wavelengths has been observed. Wavelength tuning over a range of 8 nm has also been achieved     

Calculation of differential gain and linewidth enhancement factorin 980-nm InGaAs vertical cavity surface-emitting lasers

The optimization of differential gain and linewidth enhancement factor within VCSEL's is required to achieve improved performance under dynamic conditions. In this paper, the differential gain and linewidth enhancement factor in an InGaAs-GaAs VCSEL have been calculated over a range of carrier densities and at various wavelengths across the gain spectrum. The results show the importance of low threshold gain values in achieving high differential gain/low linewidth enhancement factor. By temperature tuning the lasing wavelength to shorter wavelengths than the gain peak, values of α_H as low as 0.6 can be achieved