A Consideration of an Optical Coupler for Optical Submarine Transmission Laser Redundancy Systems

Theoretical and experimental results are described for a new optical coupler which consists of two laser diodes, two GRIN spherical rod lenses, a polarizing filter, and a single-mode fiber, and which employs laser diode polarization characteristics for an optical submarine transmission laser redundancy system. This optical coupler has two channels at 1.3 μm wavelength. Optical coupler loss values, which include coupling loss, polarization loss, and assembly loss, are 4.9 dB for one laser diode and 5.2 dB for another laser diode. Such loss values are almost the same as the conventional laser diode module loss for a single-mode fiber. This paper describes in detail a laser redundancy system in an optical submarine transmission system, structure and characteristics of an optical coupler, and experimental results on a high bit rate long-haul transmission system using the proposed optical coupler.     

Highly Symmetric Optical Fiber Tapers Fabricated With a CO2 Laser

This letter presents a simple technique that improves the symmetry of tapered fibers fabricated with a continuous-wave CO₂ laser. The uniform heat distribution inside an optical fiber is achieved by using a nonscanning dual-spot laser beam which applies heat on two sides of the optical fiber simultaneously. In so doing, highly symmetric tapers are obtained with an ellipticity close to unity. These tapers can be used as low-loss and polarization-dependent loss optical fiber filters or other optical devices such as symmetric fibers lenses     

Coherent optical frequency domain reflectometry (OFDR) using afiber grating external cavity laser

An optical frequency domain reflectometry (OFDR) system containing a narrow linewidth fiber grating external cavity laser is demonstrated to have 62-dB of sensitivity when detecting Fresnel backreflection and 2 m of resolution at a 115 m range in optical fiber. With this system we were able to detect Rayleigh backscattering in optical fiber with 20-dB signal-to-noise ratio. The phase noise limitation on the distance range for the OFDR was investigated, and the measured signal-to-noise ratio (SNR) data followed the theoretical simulation over the ranges measured. This technique has potential to be applied to the OFDR at 1550 mm with very high dynamic range by using an erbium doped fiber laser     

Femtosecond Laser Application to PLC Optical Devices and Packaging

Using tightly focused femtosecond laser pulses, we produce an optical waveguide and devices in transparent materials. This technique has the potential to generate not only channel waveguides, but also three‐dimensional optical devices. In this paper, an optical splitter and U‐grooves, which are used for fiber alignment, are simultaneously fabricated in a fused silica glass using near‐IR femtosecond laser pulses. The fiber‐aligned optical splitter has a low insertion loss, less than 4 dB, including an intrinsic splitting loss of 3 dB and excess loss due to the passive alignment of a single‐mode fiber. Finally, we present an output field pattern, demonstrating that the splitting ratio of the optical splitter becomes approximately 1:1.     

Thermal optical bistability in InGaAs/InAlAs MQW etalons at 1.5 mu m wavelength

The authors report on the fabrication of devices assembled in one unit and the observation of thermal optical bistability with low threshold and high reproducibility using the low-energy side of a 1.54- mu m etalon peak. The devices are InGaAs/InAlAs multi-quantum-well (MQW) nonlinear etalons, whose finesse of 20 was obtained by using a SiO/sub 2//TiO/sub 2/ high-reflectivity coating. The authors also show that the nonlinear characteristics depend on the wavelength of the incident light detuned from the etalon peak. The relation between optical bistable characteristics and incident beam wavelength is studied in detail using a tunable F-center laser.<>     

Improved coupling efficiency of a strained InGaAs-AlGaAs quantum-well laser into a fiber Bragg grating

We describe a highly efficient coupling of up to 78% into a single mode fiber (SMF) by utilizing a low-divergence-angle InGaAs-AlGaAs laser and a new high-NA aspheric lens, resulting in the coupled optical output of over 300 mW with a kink-free performance. The kink-free 300 mW of fiber-coupled power is the largest power reported from a diode laser wavelength stabilized using a fiber Bragg grating. A 3% fiber Bragg grating makes the optical output stabilize at a wavelength of 1.016 /spl mu/m for an optical output power up to 310 mW and without any distinct decrease of the optical output. The coupling tolerance for lateral offsets is improved by utilizing a thermal-diffused expanded-core technique even in the case of using a high-NA coupling aspheric lens. We have also achieved a 300-mW fiber-coupled wavelength-stabilized InGaAs-AlGaAs semiconductor laser butterfly module using a fiber Bragg grating.     

Laser-to-fiber coupling scheme by utilizing a lensed fiberintegrated with a long-period fiber grating

An optical coupling scheme between a laser diode and a single-mode fiber utilizing a lensed fiber integrated with a long-period fiber grating is experimentally demonstrated and qualitatively analyzed. A long working distance of 110 μm and a coupling of 35% are obtained for a laser diode with an ellipticity of 2.5. The longitudinal and transverse tolerances at 1-dB excess loss are 26 and 2.5 μm, respectively     

Optical coupling characteristics of laser diodes to thermally diffused expanded core fiber coupling using an aspheric lens

A discussion is presented of the optical coupling characteristics of a 1.3 mu m laser diode to a thermally diffused expanded core (TEC) single-mode fiber coupling using an aspheric lens. The misalignment tolerance width for a 0.5 dB loss increment of the expanded core fiber was enlarged to 8.4 mu m from 1.9 mu m of a nonexpanded core fiber without a remarkable coupling-loss increase. The TEC fibers will make the LD module assembly easier, and reduce the assembly cost.<>     

Polarization control on output of single-mode optical fibers

Polarization control of the light output from single-mode fiber systems is very important in order to connect it to polarization-dependent integrated optical circuits and applications using a heretodyne detection system. In this paper, automatic control of the polarization of light transmitted through the fiber was demonstrated by an electrooptical and electrical feedback system. In this system, we used a 1.6 μm long wavelength semiconductor CW BH laser, low-loss single-mode optical fiber with a loss of 0.2 dB/km, and two thinz-cut LiNbO3modulators tilted 45° relative to each other. The output light from this polarization controller was maintained to be linear while that from the single-mode fiber was unstable and elliptically polarized.     

掺Yb3+双包层石英光纤的研制及其激光特性

用MCVD工艺加溶液掺杂法研制成功了大几何尺寸、大数值孔径内包层的掺Yb3+双包层石英光纤,内包层直径125μm,数值孔径达0.36.完成了包层抽运光纤激光器的初步实验,在波长1.06μm处获得220mW的激光输出,光-光转换效率为26%.     

First sea trial of 1.5-μm submarine optical fiber cable

The first sea trial of submarine optical fiber cable using dispersion-shifted fibers is described. The discussion covers the fiber structural design, cable manufacturing results, fiber splicing, cable laying results, and a high-accuracy measurement technique for optical loss and chromatic dispersion. The results demonstrate the feasibility of long-span, high-capacity 1.5-μm submarine optical fiber cable     

Measurement of propagation constants related to material properties in high-bandwidth optical fibers

The material contribution to group index and material dispersion were measured in high-bandwidth graded-index optical fibers. A shuttle-pulse technique provided measurements of group index with precisions and accuracies of 0.1 and 0.2 percent using 5 m lengths of optical fiber. Material dispersion in fibers was measured over the0.8-0.9 mum wavelength region using different wavelength, short-pulse laser diodes. The influence of material dispersion on fiber bandwidth measurements was evaluated for laser diode sources. Limitations arising from source linewidth were experimentally determined from measurements on a fiber with high microbending enhanced bandwidth.     

大长度高精度侧面研磨光纤关键技术及应用

自主研制了光纤轴向研磨厚度精确控制装置和电弧放电光纤研磨截面高精度抛光装置.通过高精度压电陶瓷PZT调节光纤侧面的研磨厚度,研磨精度达0.01 μm.通过定位传感器控制光纤的研磨长度,可实现长度大于100 mm的光纤侧面研磨.采用低热膨胀系数微晶玻璃作为研磨块.大大降低研磨损耗.微晶玻璃上刻制多个V型槽,可实现多光纤同时轴向研磨,极大地提高了光纤研磨效率.利用电弧放电所产生的高温将研磨光纤的表面进行熔化,从而有效消除研磨光纤表面的粗糙度,抑制微裂纹或凹坑造成的较大损耗.利用上述装置,可精确控制光纤侧面研磨厚度,为高精度双折射可控保偏光纤光栅、基于光纤光栅辅助耦合波分复用(WDM)下话路器等光器件的研究奠定了基础.     

Utilization of electroplating to lock fibers for use in opticaldevice packaging

An electroplating technique for permanently fixing single-mode fibers into position in optical device packages is described. In this technique, the fiber is mounted in a metal tube and aligned to an optical device mounted on a metal substrate. The fiber is in close proximity to the substrate and a flexible conductive gel is used to connect the two electrically. The fiber, gel, and substrate thus form the plating cathode. When immersed in a plating bath with an anode inserted, metal can be deposited across the gel, forming a strong metal bridge between the fiber and substrate, locking the fiber into position. Under appropriate conditions, misalignments within ±1 μm during the plating process have been observed. This technique was used to package a laser diode transmitter, which locked the laser-to-fiber alignment to within 0.7 μm, or 0.1 dB of the optimum coupled power     

A 10-Gb/s optical transmitter module with a monolithicallyintegrated electroabsorption modulator with a DFB laser

A compact 10-Gb/s optical transmitter module with small-chirp output was developed by using a monolithically integrated electroabsorption modulator with a distributed-feedback laser. This module can be operated at a bit rate of more than 10 Gb/s at 1.55 μm, and shows a high modulated output power of ~1 dBm with a low optical coupling loss of 3.2 dB between chip and fiber. A multifunctional and compact optical isolator with a monitor photodiode was also developed to decrease noise     

高功率密度光纤激光元器件传输特性测试系统

为了提高高功率密度下光纤激光元器件传输特性测量精度,采用基于光纤标准测试方法的双光路测量结构,设计了自动光功率比测量系统。对双光路系统的特点进行了理论分析和实验验证。利用固体微晶片激光器作为光源输出,建立了折射率匹配法传输特性测试仪实验装置,对掺镱双包层光纤的传输损耗特性进行了测量。实验中测得35m长掺镱双包层光纤对1064nm光的插入损耗为2.645dB,测得100组数据对应的标准偏差为0.026dB。并在不同的条件下进行了多次重复实验,重复测量误差不超过0.07dB。这一结果对于提高光纤激光元器件测试精度是有帮助的。     

Effects of thermally induced optical fiber shifts in V-groove arrays for optical MEMS

Thermally induced optical fiber shifts in the joints consisting of an optical fiber, epoxy adhesive and silicon substrate were simulated using a FEA (finite element analysis) package. Experiments using a real-time micro-moiré system were also performed at temperatures of 25, 40, 60, 85 and 100 °C for confirmation of the FEA results. The optical coupling loss, caused by the fiber shifts, of a single-mode fiber to fiber and a laser diode to a fiber was studied. The results revealed that thermally induced fiber shifts increased with the number of V-groove channels. The optical coupling loss is the greatest during thermal loading for the outer fiber in the four channels V-groove array. Optical losses of 0.334 and 0.346 dB for fiber-to-fiber coupling and 1.54 and 1.56 dB for laser diode to fiber coupling were calculated using the fiber shift values obtained from the FEA and experiments, respectively, for the outermost fiber joint in the four channels V-groove array at 100 °C. The effects of fiber shifts especially the shift of the fiber that is positioned at the outermost V-groove in the array cannot be ignored.     

激光直写技术制备SiO2-TiO2条形光波导工艺研究

为了研究激光直写技术在光波导制备中的应用,采用波长为1.07μm的连续光纤激光器制备了硅基SiO2-TiO2条形光波导。探讨了激光直写技术制备条形光波导的原理,研究了激光参数对条形光波导宽度的影响,最后测试了光波导的通光模场以及光传输损耗。结果表明,条形光波导的宽度随着激光功率密度的增加而增大。当激光扫描速率在0.1mm/s~1mm/s范围内变化时,条形光波导的宽度随着激光扫描速率的增加而降低;高于1mm/s时对波导宽度无明显影响。在优化的工艺参数下,激光直写得到的条形波导的厚度约为0.4μm,宽度为120μm,整条波导非常均匀、准直性很好,对于1550nm波长的光呈多模传输,最小传输损耗为1.7dB/cm。     

1.7 μm全光纤锁模脉冲掺铥光纤激光器研究

1.7 μm超短脉冲光纤激光器在生物成像和材料加工等领域具有重要的应用前景,受到了科学家们的极大关注。基于非线性偏振旋转锁模技术,实验搭建了全光纤结构的1.7 μm锁模脉冲掺铥光纤激光器。通过在激光器内加入光纤滤波器抑制掺铥光纤中的长波激光发射,同时采用纤芯泵浦的方式有效获得了1.7 μm波段的增益。激光器输出脉冲的光谱中心波长为1733 nm,3 dB带宽为6.3 nm。锁模脉冲的重复频率为19.56 MHz,平均功率为1.4 mW。同时,数值模拟了脉冲在激光器的腔内演化。文中提出的1.7 μm全光纤锁模激光器有利于进一步提高1.7 μm激光源的稳定性和集成度,在生物成像等领域具有重要的应用价值。     

Simultaneous Measurements of Dispersion Parameter and Fiber Length Using the Self-Seeding Laser Oscillation of a Fabry–PÉrot Laser Diode

A simultaneous measurement technique of the dispersion parameter and the length of an optical fiber has been demonstrated by using the self-seeding laser oscillation of a Fabry-Perot laser diode. We measured the dispersion parameter and the length of an optical fiber from the modulation frequency changes required to induce single-mode laser oscillations through an optical closed-loop path. The dispersion and fiber length measurements were within 1.5% and 0.2%, respectively, of the values measured by commercial instruments.