Bias point thermal shift growth in Z-cut LiNbO/sub 3/ Modulators

Growth of a bias point thermal shift induced by dc bias in z-cut LiNbO/sub 3/ optical intensity modulators is quantitatively discussed from the standpoint of its impact on field service. During 20 years of device operation under a worst-case dc bias condition, the thermal shift slope grows almost symmetrically with respect to a bias polarity. An initial small thermal shift of around /spl plusmn/7 mV//spl deg/C (3/spl sigma/ distribution bounds) increases continuously over time with biased operation at 55/spl deg/C and approaches /spl plusmn/70 mV//spl deg/C after 20 years. This increased temperature sensitivity would generate approximately a 2-V bias point shift toward the bias rail when modulator is exposed to temperature variation from 55/spl deg/C to 25/spl deg/C.     

DC-Voltage-induced thermal shift of bias point in LiNbO/sub 3/ optical Modulators

Increasing thermal shift of a bias point is observed when dc voltage is applied to z-cut LiNbO/sub 3/ (LN) modulators having asymmetric design; whereas, stable thermal shift is observed in symmetric x-cut LN modulators. A growth of the thermal shift depends upon the amplitude, polarity, and duration of the applied voltage and constitutes a new criterion to reliability modeling of LN modulators.     

双二进制调制在高速LiNbO3光调制器上的实验实现

通过实验方式在LiNbO3光调制器上实现了比特率为11.3 Gb/s的光信号的双二进制调制格式,测试并分析了相关的实验参数,包括调制前后的电眼图、光眼图,以及经过长距离光纤传输后的性能编号及比较等.实验证明,经过双二进制调制后的光信号经过长距离传输后较未调制的光信号眼图具有明显的改善.     

Interferometric-type polarisation splitter on Z-propagating LiNbO/sub 3/:Ti

A new optical waveguide TE-TM mode-splitter realised on X-cut, Z-propagating lithium niobate is reported. At 1.52 mu m, the device exhibits extinction ratios better than 18 dB for applied voltages lower than 20 V, and can be used as a polarisation switch.<>     

First order quasiphase matching in LiNbO/sub 3/

First order quasiphase matched second harmonic generation in LiNbO/sub 3/ channel waveguides is experimentally demonstrated and compared with theoretical estimation. Conversion efficiencies of 11%/W for 1 cm long interaction length were measured for the generation of 435 and 450 nm blue light, which is the same order of magnitude as calculated for the structure.<>     

Optical gain in proton-exchanged Cr:LiNbO/sub 3/ waveguides

The authors report on a study of optical gain in chromium-doped LiNbO/sub 3/ waveguides formed by the proton-exchange process. Optical gain in proton-exchanged Cr:LiNbO/sub 3/ channel waveguides has been measured for the first time. These waveguides show potential for diode-laser pumping of an integrated, broadband tunable laser in the 750-1150 nm spectral range.<>     

Ti:LiNbO/sub 3/ digital optical switch matrices

Optical switch matrices were implemented using low drive voltage digital optical switches as switching elements. A drive voltage of 25 V for polarisation independent operation was achieved in a 4*4 switch. An 8*8 switch with low drive voltage could be achieved by assigning the proper lengths for switching elements.<>     

Continuous-wave erbium-diffused LiNbO/sub 3/ waveguide laser

The first integrated optical laser in LiNbO/sub 3/, doped by an indiffusion of Er/sup 3+/ prior to channel-guide fabrication by Ti diffusion is reported. Pumped by a colour centre ( lambda /sub p/=1.477 mu m), CW operation at lambda =1.532 mu m ( Delta lambda approximately 0.3 nm) with a threshold of approximately 8 mW absorbed power was achieved.<>     

DC drift of X-cut LiNbO/sub 3/ modulators

DC drift of unbuffered dc bias electrode port of x-cut LiNbO/sub 3/ (LN) modulators is investigated. Unlike buffered LN modulators, their dc drift is irreversible and relatively suppressed after biased aging. Additionally, they show rolling-over-type drift and do not drift divergently. Extended temperature-voltage accelerated drift tests find temperature activation energy of 1.2 eV and a proportional relationship between drift rates and initially applied bias voltages. Such drift behaviors characteristic of unbuffered x-LN can demonstrate their high reliability with respect to dc bias drift.     

Reliability of nonhermetic bias-free LiNbO/sub 3/ modulators

Reliability for nonhermetic bias-free LiNbO/sub 3/ optical modulators is estimated from aging data in both dry and damp heat conditions. The two dominant failure modes for these devices are: 1) device performance degradation due to temperature-activated drift of the annealed proton-exchange waveguide; and 2) optical insertion loss increase due to humidity-induced deterioration of glued fiber joints. A total failure rate of 30 failures in time (FITs) is predicted for 20 years operation at 45/spl deg/C and moderate humidity conditions (40% RH). This estimate based on laboratory-test data is consistent with a field failure rate <5 FITs observed in fielded devices.     

DC drift of Z-cut LiNbO/sub 3/ modulators

DC drift characteristics of z-cut LiNbO/sub 3/ modulators with oxide buffer layers were studied with respect to their acceleration factors and long-term reliability. Analysis of more than 120 data points of measured drift tests indicate a slight nonlinear contribution by the starting bias voltage Vs to drift acceleration, with a factor equal to Vs/sup 1.27/. However, the observed nonlinearity is shown to have little affect on reliability estimations due to a dominant contribution from temperature activation energy; Ea=1.1 eV. The dc drift failure rates are estimated to be on the order of tens of failures in time for 20 years at 55/spl deg/C.     

M-Z型LiNbO3外调制器的优化设计分析

阐述了以M-Z干涉型光波导为波导结构、铌酸锂(LiNbO3)材料电光效应为基础的集成光学强度调制器的工作原理及器件结构,讨论了集成光学强度调制器性能指标,重点讨论了干涉型行波电极结构LiNbO3外调制器的优化设计思想。     

Proton-exchanged optical waveguides in LiNbO/sub 3/ using octanoic acid

Low-loss proton-exchanged planar waveguides in z-cut LiNbO/sub 3/ were fabricated and characterized optically using octanoic acid as a proton source. The waveguide exhibited a step-index profile with an index change of 0.118 measured at 0.633 mu m. The lowest waveguide propagation loss measured was 1.2 dB/cm, and it was reduced further to 0.4 dB/cm after annealing. The diffusion rate and the activation energy using this acid were found to be lower than those reported using other acids.<>     

Proton-exchanged LiNbO/sub 3/ optical waveguides using stearic acid

Proton-exchanged optical waveguides have been fabricated in z-cut LiNbO/sub 3/ using a new proton source: stearic acid. These waveguides were characterized optically and were found to exhibit a step index profile with Delta n=0.118 measured at 0.633 mu m. The propagation losses were typically around 1.5 dB/cm, and the diffusion constant and the activation energy for the proton-exchange process were measured to be 5*10/sup 6/ mu m/sup 2//h and 69 kJ/mol, respectively.<>     

LiNbO/sub 3/ Mach-Zehnder modulators with fixed negative chirp

Negative chirp modulation of optical transmitters is needed for the optimal performance of high bit-rate transmission in optical fiber systems operating at nonzero dispersion window at 1.5 /spl mu/m. In this paper several approaches to achieving any fixed chirp value for LiNbO/sub 3/ modulators are proposed, Experimental results of impedance matched devices on x-cut lithium niobate with chirp values of /spl plusmn/0.7 and /spl plusmn/1.0 are presented. By tuning the modulators bias point, the chirp value can be adjusted linearly around the designed value without degrading other performances.     

Low drive-power integrated acoustooptic filter on X-cut Y-propagating LiNbO/sub 3/

The authors fabricated very low power integrated acoustically tunable optical filters using walkoff-compensated miniature interdigital transducers, coupled to narrow-width acoustic waveguides. Nearly 100% transverse electric-transverse magnetic (TE-TM) polarization conversion efficiency was achieved using only 8 mW of applied RF power in a 1550-nm filter of 1.8-nm optical bandwidth. A power handling capacity of almost 100 channels was demonstrated by driving these transducers with 760 mW of RF power. These devices suffer little performance degradation in terms of filter width and sidelobe spectrum.<>     

Laser oscillation of single-mode channel waveguide in Nd:MgO:LiNbO/sub 3/

Laser oscillation in an Nd:MgO:LiNbO/sub 3/ single-mode channel waveguide has been demonstrated. Under IR dye laser pumping, a threshold of 1.5 mW and a slope efficiency of 14% were achieved. Laser oscillation has also been observed with diode pumping.<>     

A method for microwave characterization of LiNbO/sub 3/ modulators

A procedure to extract the S-parameters of both the active section and the input and output coplanar tapers of Mach-Zehnder modulators is proposed. The S-parameters of the three sections of the modulator have been successfully extracted up to 30 GHz from measurements and EM simulations performed on proper test structures.     

基于铌酸锂调制器的超短光脉冲源的研究

提出了一种基于商用化的铌酸锂调制器产生超短光脉冲的方法.直流光依次经过相位调制器和强度调制器调制,利用色散补偿光纤(DCF)和梳状色散光纤链(CDPF)对调制产生的光脉冲分别进行啁啾补偿、非线性压缩.压缩后的光脉冲注入高非线性光纤(HNLF),利用其自相位调制效应(SPM)展开脉冲光谱后滤波,可以有效地消除光脉冲的基座,实现光脉冲的整形.获得了10GHz的1.8ps无基座近变换极限光脉冲.