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This paper presents the design, fabrication, and measurement results of a 2×2 microelectromechanical systems optical switch. The switch comprises an electromagnet and lensed fibers assembled with a micromachined movable vertical micromirror. The optical switch utilizes the out-of-plane motion of the vertical micromirror actuated by electromagnetic force compared to the comb-driven linear actuation achieved by the electrostatic force. At a wavelength of 1550 nm, the insertion loss of 0.2-0.8 dB and the polarization-dependent loss of 0.02-0.2 dB are measured. The switching time is 1 ms. A novel method of realizing a latchable optical switch using an electromagnetic actuator is also provided and verified. The latch mechanism is based on the latchability of the electropermanent magnet instead of the mechanical one using conventional arch-shaped leaf springs. [ABSTRACT FROM PUBLISHER]

A family of thin film interference filters is described that incorporates amorphous silicon layers for wide thermo-optic tunability and the potential for multiple cavity designs. Plasma enhanced chemical vapor deposition (PECVD) of hydrogenated amorphous silicon (a-Si:H) onto fused silica or crystalline silicon wafer substrates produces films with high index (n=3.71), low loss at 1500 nm (k<4×10-6), and thermo-optic index coefficients approximately ten times larger than those of the dielectric materials typically used in wavelength division multiplexing (WDM) filters. Pairing amorphous silicon with low index (n=1.77, k=1×10-6) silicon nitride companion layers followed by post-process annealing leads to multilayer film stacks which may be cycled up to 400 C without delamination or failure, resulting in thermal index modulations as large as 4% and enabling a wide variety of dynamic thin film device designs. In this paper we survey the range of device applications and show experimental demonstrations for two quite different classes of functionality. One class of filters is tunable in wavelength in the conventional sense. Single and dual-cavity narrowband filters are described with temperature coefficients of center wavelength 85-172 pm/°C in the 1550 nm WDM band and tuning ranges as large as 60 nm, an order of magnitude larger thermal tunability than for conventional thin film narrowband filters. A second class of filters is fixed in wavelength but switchable in transmission, based on hybrid structures which combine tunable semiconductor films and cavities with static dielectric films and cavities in an integrated coating design. To demonstrate the principle of a switchable add/drop filter, we fabricated a five-cavity, 117 layer, 200 GHz filter by combining a single cavity of a-Si:H/a-SixNy films deposited by PECVD with four cavities of dielectrics Ta2O5/SiO2 deposited by ion assisted e-beam evaporation. By varying the temperature, this device can be switched thermo-optically between transmission and reflection states at a fixed channel 1548.3 nm with a contrast ratio 18.4 dB. Stable devices can be obtained even with large internal temperature changes in microscopic volumes provided that layer- -to-layer and layer-to-substrate adhesion is robust, film stresses are well controlled through coefficients of thermal expansion matching, and devices are annealed at or above maximum operational temperatures. "Hitless" filters can be obtained by structuring thermo-optic filters in two independently heated portions. Thermo-optically actuated thin film semiconductor devices are manufacturable and testable on a wafer scale and may be packaged by methods adapted from those for conventional thin film filters. [ABSTRACT FROM PUBLISHER]

Single-mode perfluoropolymer waveguide structures exhibiting a polarization-independent ultra low loss of <0.05 dB/cm at 1310 nm and <0.07 dB/cm at 1550 nm with a Δn of 1.6% have been fabricated for the first time. These new low-loss structures indicate relatively high-power-handling reliability at 1310 and 1550 nm. Based on this, a highly efficient arrayed-waveguide grating multi-demultiplexer with a crosstalk of 30±2 dB and an insertion loss of 2.8±0.3 dB is realized. [ABSTRACT FROM PUBLISHER]

We present a compact integrated fiber laser with more than 200 mW of output power. It combines polarized fiber output with very narrow linewidth of less than 2 kHz. The coherence length of the laser is measured to be longer than 5 km. The laser features high mode stability of less than ±10 MHz over hours. The relative intensity noise (RIN) spectrum is dominated by a peak at the relaxation oscillation frequency and is shot-noise limited otherwise. The RIN peak at 1 MHz is reduced to ∼-130 dB/Hz by integrating a negative feedback circuit. In addition to thermal wavelength tuning, the laser frequency can be modulated at a bandwidth of up to 10 kHz via the piezoelectric effect. [ABSTRACT FROM PUBLISHER]

We have succeeded in fabricating a low-loss and long length photonic crystal fiber (PCF) by improvement of fabrication process. The fiber is 10 km long and has a lowest loss of 0.37 dB/km at 1550 nm ever reported. We also succeeded in reducing the OH absorption loss to 3 dB/km. This is almost the half of the value ever reported. Using the low-loss PCF, we performed the first DWDM transmission experiment. DWDM signal of 8×10 Gbit/s is successfully transmitted through the PCF. [ABSTRACT FROM PUBLISHER]

A polymer containing fine droplets of liquid crystal (LC) is investigated for obtaining an optical phase-shifting attenuator at 1550-nm wavelength. Two mixtures of liquid crystals and monomers are compared for a cell thickness of 15 μm. The first method uses nanosized LC droplets to achieve 2.29-rad phase shifting for an applied voltage of 230 Vrms. The second method uses microsized LC droplets to achieve 2.35-rad phase shifting for an applied voltage of 15 Vrms. Theoretical analysis of the phase shifting is developed. This optical property is used to achieve a variable optical attenuator (VOA) between two single-mode fibers. An optical architecture using graded index rod lenses and a pattern of photoresist polymer is presented. Typical characteristics of such VOA are: 12-dB range of attenuation, a maximum polarization dependence loss of 0.5 dB, 1.1-dB insertion loss, and a saturation voltage of 20 Vrms. [ABSTRACT FROM PUBLISHER]

An intensity modulation using a hybrid electrooptic (EO) polymer/sol-gel straight channel waveguide, useful in the 1550-nm wavelength regime is demonstrated without using Mach-Zehnder interferometric waveguide. The sol-gel waveguide is selectively buried so that a vertical transition into and out of an EO polymer coated on the sol-gel waveguide is arranged. The throughput ratio for transverse electric (TE) and transverse magnetic (TM) modes of the light coupled out of the hybrid waveguide is improved up to 0.9 dB with the help of reduced birefringence of the EO polymer after corona poling. We show that the fabrication process of such hybrid-type waveguides enables production of a phase modulator operating at 1550-nm wavelength. The fabricated straight channel waveguide modulator exhibits stable- and high-intensity modulation efficiency (82%) using a simple cross-polarization setup after the polarization dependence is reduced. We demonstrate an all wet-etching process to fabricate polymeric EO modulators. [ABSTRACT FROM PUBLISHER]

This paper reports our investigation on widely tunable fiber-ring lasers and broadband amplified spontaneous emission (ASE) light sources with thulium-doped fluoride fibers (TDFs). The experimental results for thulium-doped optical fiber amplifiers will also be discussed. We achieved widely tunable fiber lasers that had tuning ranges of 94 nm with 1550 nm + 1050 nm pump configurations and of 85 nm with 1550 nm + 1400 nm pump configurations, respectively. It was observed that the lasers oscillated under multilongitudinal-mode operation with linewidth of 400 MHz, signal-to-source noise ratio of 60 dB, and power stability of 0.003 dB for a laser output of 1 mW. A broadband ASE source with a power density of more than -15 dBm/nm between 1465 and 1535 nm was also demonstrated with a novel hybrid configuration by using both TDF and erbium-doped fiber. [ABSTRACT FROM PUBLISHER]

In this paper, we report on the design of a compact (≍ 226 μm) on-chip InGaAsP/InP polarization converter based on an asymmetric rib waveguide. Our theoretical analysis demonstrates that the device displays a conversion efficiency of < -25 dB (> 99.68% power conversion between orthogonal polarization) at 1550-nm wavelength with a nearly flat response over the optical C band. Regarding fabrication tolerances, we predict that the most sensitive design parameter is the waveguide width as the conversion efficiency drops to 10 dB for a deviation of ± 0.1 μm from the optimized value. [ABSTRACT FROM PUBLISHER]

We propose a simple method of characterizing the sensitivities of the cladding modes of an optical fiber to environmental conditions through the analysis of a single device. These sensitivities to conditions such as temperature, strain, and the refractive index of the surrounding medium are of particular relevance to the fabrication of long-period gratings (LPGs). The inferred sensitivities are all valid around the design wavelength of the analyzed fiber Bragg grating (FBG) device, and so can provide important design information for the manufacture of a LPG device that couples to a single or several cladding modes. To demonstrate the method, we use a FBG with a design wavelength of 1550 nm to determine the sensitivity of the cladding modes of a standard telecomm fiber to both temperature and strain. Using this information we infer the environmental sensitivity of any LPG fabricated in this fiber that operates around this wavelength. We design and fabricate LPGs to couple to selected cladding modes and measure the sensitivities of these devices directly. We find good agreement between the directly measured and inferred sensitivities. [ABSTRACT FROM PUBLISHER]

We have developed a microlaser encoder that can detect displacements relative to an external grating scale with a resolution on the order of 10 nm. Its size is only a few tens of a percent of a conventional encoder's. A long-lasting InP laser diode with a wavelength of 1550 nm was bonded, along with several photodiode chips, within an alignment accuracy of 1 μm onto a silicon planar lightwave circuit chip. The chip is 2.3 mm × 1.7 mm and includes a fluorinated polyimide lightwaveguide fabricated in advance. A wide gap of more than 600 μm was obtained between the external grating scale and the encoder despite the tiny size of the sensor. When used as a rotary encoder, the number of rotations could also be detected. Thus, this microencoder satisfies the market requirements for practical use. [ABSTRACT FROM PUBLISHER]

We have demonstrated the transmission performance of 10-Gb/s transmitters based on LiNbO3 modulator using semiconductor optical amplifiers (SOAs) as booster amplifiers. Utilizing the negative chirp converted in SOAs and self-phase modulation induced by high optical power, we can successfully transmit 10-Gb/s optical signals over 80 km through the standard single-mode fiber with the transmitter using SOAs as booster amplifiers. SOAs can be used for booster amplifiers with a careful adjustment of the operating conditions. In order to further understand an SOA's characteristics as a booster amplifier, we model SOAs and other subsystems to verify the experimental results. Based on the good agreement between the experimental and simulation results, we can find the appropriate parameters of input signals for SOAs, such as extinction ratio, rising/falling time, and chirp parameter to maximize output dynamic range and available maximum output power (Po,max). [ABSTRACT FROM PUBLISHER]

A rapidly tunable, polarization-independent, low-loss optical add-drop multiplexer (OADM) for the 1550-nm wavelength regime is reported. The four-port device consists of two input waveguides, a polarization beam splitter (PBS), two polarization conversion/electrooptic tuning waveguide sections, a second PBS and two output waveguides. The waveguides, which are single mode for both TE and TM polarizations, are fabricated on a LiNbO3 substrate by Ti diffusion. Spectral selection is based on phase-matched polarization conversion due to shear strain induced by a dielectric grating overlay film. An applied voltage tunes the device by changing the waveguide birefringence and hence the optical wavelength at which most efficient polarization conversion occurs. Tuning of 0.1 nm/V with a maximum range of 24 nm has been obtained. A tuning speed of 50 ns, corresponding to a rate of 0.128 nm/ns, has been achieved. Channel isolation is better than 24 dB. Fiber-to-fiber insertion loss <5.4 dB has been obtained and polarization independent loss (PDL) of 0.24 dB for both drop and through ports have been realized over the tuning range. Thermal tuning has also been demonstrated. [ABSTRACT FROM PUBLISHER]

A high-output-power 1550 nm polarization-insensitive semiconductor optical amplifier (SOA) was developed for use as a compact in-line optical amplifier. A very thin tensile-strained bulk structure was used for the active layer and active width-tapered spot-size converters (SSCs) were integrated on both input and output sides. The SOA module exhibited a high saturation output power of +17 dBm together with a low noise figure of 7 dB, large gain of 19 dB, and low polarization sensitivity of 0.2 dB for optical signals of 1550 nm wavelength. For the amplification of optical signals modulated at 10 Gb/s in the nonreturn-to-zero (NRZ) format, a good eye pattern without waveform distortion due to the pattern effect was obtained at an average output power of up to +12 dBm. Additionally, good amplification characteristics were demonstrated for the signal wavelength range corresponding to the C-band. [ABSTRACT FROM PUBLISHER]

We present a metal-organic-chemical-vapor-deposition-grown low-optical-insertion-loss InGaAsP/InP multiple-quantum-well electroabsorption modulator (EAM), suitable for both nonreturn-to-zero (NRZ) and return-to-zero (RZ) applications. The EAM exhibits a dynamic (RF) extinction ratio of 11.5 dB at 1550 nm for 3 Vp-p drive under 40-Gb/s modulation. The optical insertion loss of the modulator in the on-state is -5.2 dB at 1550 nm. In addition, the EAM also exhibits a 3-dB small-signal response (S21) of greater than 38 GHz, allowing it to be used in both 40-Gb/s NRZ and 10-Gb/s RZ applications. The dispersion penalty at 40 Gb/s is measured to be 1.2 dB over ±40 ps/nm of chromatic dispersion. Finally, we demonstrate 40-Gb/s transmission performance over 85 km and 700 km. [ABSTRACT FROM PUBLISHER]

Micro-ring wavelength filters and resonant modulators using polymer materials at 1300 nm and 1550 nm are analyzed, designed, and demonstrated. The rings are integrated with vertically coupled input and output waveguides. The devices are fabricated using optical lithography. Filters with a finesse of 141 and free spectral range of 5 nm at 1300 nm and finesse of 117 with a free spectral range (FSR) of 8 nm at 1550 nm are demonstrated. Ring resonators with a Q as high as 1.3 × 105 at 1300 nm are demonstrated. The filters can be temperature tuned at the rate of 14 GHz/°C. Resonant ring modulators, which use an electrooptic polymer, are demonstrated. The resonance wavelength voltage tunes at the rate of 0.82 GHz/V. The modulators have a bandwidth larger than 2 GHz. Using the resonant modulator, and open eye diagram at 1 Gb/s is demonstrated. [ABSTRACT FROM PUBLISHER]

In this paper, we discuss the conditions under which we can correctly extract a variety of module parameters of single mode bidirectional optoelectronic duplexer and diplexer modules during relatively slow thermal cycling between -40°C and +85°C. The obtained values of parameters such as tracking error, optical crosstalk, and the laser diode characteristic temperature have been compared for bidirectional modules from different manufacturers and the impact on these parameters of different interconnect techniques, like microoptic (Mo), silicon optical bench, and planar lightwave circuit technologies is discussed. It is shown that there is a conflict between small threshold currents and good temperature stability for InGaAsP-based Fabry-Perot laser diodes emitting at 1300 and 1550 nm. Then the results of spatially low coherence reflectometry for the different bidirectional module types are presented. [ABSTRACT FROM PUBLISHER]

An experimental demonstration of an energy limiter for short pulses at 1550 nm is reported. The limiter is based on an optical fiber Sagnac loop with an intraloop dichroic saturable absorber based on an InGaAsP-based waveguide with compressively strained multiple quantum wells. The saturable absorber is placed asymmetrically in the loop and is used as a Kerr-like nonlinear phase shifter. The device is operated in a novel dual polarization scheme, which offers some unique advantages. Excellent limiting for noise reduction purposes is demonstrated with the device. [ABSTRACT FROM PUBLISHER]

We report on a commercially reproducible silicon wafer with a high-reflectance buried distributed Bragg reflector (DBR). The substrate consists of a two-period DBR fabricated using a double silicon-on-insulator (SOI) process. The buried DBR provides a 90% reflecting surface. We have fabricated resonant cavity-enhanced Si photodetectors with 40% quantum efficiency at 860 nm and a full-width at half-maximum of 29 ps suitable for 10 Gbps data communications. We have also implemented double-SOI substrates with 90% reflectivity covering 1300 and 1550 nm for use in Si-based optoelectronics. [ABSTRACT FROM PUBLISHER]

Vertically coupled, wafer-bonded III-V semiconductor waveguide devices provide a means to obtain more powerful, compact photonic integrated circuits and allow for the combination of different materials onto a single chip. Various switching, filtering, multiplexing, and beam splitting devices in the InP-InGaAsP and GaAs-AlGaAs systems for signals in the 1550-nm range have been realized. An investigation of optimal optical add-drop multiplexer waveguide layout shapes has been performed through integration of the coupled-mode Riccati equation, providing potential sidelobe levels of less than -32 dB and filter bandwidths over 20% narrower than those of previous devices. Effects of nonideal processing conditions on filter performance are analyzed as well. [ABSTRACT FROM PUBLISHER]

We measured the continuous wave (CW) laser-induced damage threshold of single-mode fiber-optic connectors at 1550 nm. Clean standard physical contact and angled physical contact connectors did not show any evidence of damage for 10 min exposures of 1 W or 3 W. Defective connectors with scratched or undercut endfaces showed identical high-power tolerance as clean connectors without defects. Samples contaminated with carbon black-doped acrylate showed drastic optical failure signatures at approximately 50 mW. Contaminated connectors with expanded mode field diameters ranging from 20 to 62 μm showed higher failure thresholds than standard connectors with 10-μm spot sizes. We observed that the optical failure threshold power level (Pfailure) increased linearly with spot size for the highly contaminated connectors used in this study. [ABSTRACT FROM PUBLISHER]

Adaptive control in combination with ultrafast pulse shaping provides a compelling approach to harness events that occur on the fastest timescale available. This paper illustrates the application of adaptive pulse shaping to femtosecond pulse propagation at λ=1550 nm in single-mode optical fibers. The approach is illustrated first by through a numerical simulation of the technique. An experimental demonstration is described. The propagation of ~200-fs pulses is successfully achieved in the nonlinear regime by suitably preshaping the input pulse using an adaptive feedback loop [ABSTRACT FROM PUBLISHER]

A mode-adapted semiconductor optical amplifier (SOA) has been fabricated and packaged. At the gain peak, 1500 nm, the fiber to fiber gain was measured to be 32.5 dB. Statistics for eight packaged devices indicate that a fiber-to-fiber gain of 26.3 dB ± 1.3 dB and a saturation output power of 12.4 dBm ± 0.4 dBm are typical at a bias of 500 mA for λ = 1550 nm. Polarization sensitivity at 1550 nm was measured to be 1.1 dB ± 0.4 dB and the transverse electric (TE) polarization state noise figure (NF) was determined to be 7.0 dB ± 0.5 dB. The coupling loss was 1.3 dB ± 0.1 dB per facet. This SOA, with a 1.3-nm filter, was used as an optical preamplifier in a 10-Gb/s return-to-zero (RZ) system testbed with a pseudorandom binary sequence (PRBS) of 231 -1. A 14.5-dB improvement in receiver sensitivity was observed at a bit error rate (BER) of 10-11 [ABSTRACT FROM PUBLISHER]

Commercially available Er-doped fibers were irradiated with 5.6 and 28 MeV protons and 60Co gamma rays, up to levels of 50 krad. White-light transmission spectra under passive conditions (no pump or signal) were measured at several radiation levels for the six types of fibers that were tested. The spectra were used to evaluate the relative radiation sensitivity of the fibers and compare gamma versus proton-induced damage for two fiber types. The amount of radiation damage for the fibers was observed to scale inversely with the Ge concentration. Samples from three of the fiber types were configured as optical amplifiers using 980-nm and 1550-nm pump and input signals. In situ measurements of the gain, noise figure, and amplified spontaneous emission (ASE) were made as a function of pump power at several levels of radiation. A computer code, based on a conventional Er-doped fiber amplifier (EDFA) model, was written to simulate performance, using input data provided by the fiber vendor and anchored to measurements made prior to radiation. A comparison between the simulations and experimental data shows that, in certain fibers where the damage is significant, the radiation-induced loss determined from amplifier measurements can be substantially less than that determined from passive transmission spectra [ABSTRACT FROM PUBLISHER]

Based on a nonlinear optical polymer with a highly nonlinear chromophore (CLD) dispersed in an amorphous polycarbonate (APC), we have developed electrooptic (EO) polymer modulators operating at 1550-nm wavelength with low loss and good thermal stability. By incorporating polymer insulation layer, push-pull poling was successfully performed without film damages. We also demonstrated that the propagation loss of the EO polymer waveguide could be reduced as low as 1.2 dB/cm at 1550 nm when the large core waveguide structure was incorporated. The long-term reliabilities of the EO polymer modulator made of CLD/APC polymer were investigated. When the modulator was hermetically sealed in an inert gas, the Vπ change of a Mach-Zehnder modulator was negligible over 30 d of operation with 20-mW exposure to the waveguide input. In the thermal stability measurement, 25% Vπ increase was observed from the sample heated to 60°C over 40 d, though the sample left at room temperature showed no decay of nonlinearity [ABSTRACT FROM PUBLISHER]

A 16×16 arrayed waveguide grating (AWG) router with a channel spacing of 0.8 nm (100 GHz) operating around the 1550-nm wavelength has been fabricated using newly synthesized fluorinated polyethers. It has a good processibility and a high thermal stability up to 510°C. The propagation loss of the buried-channel waveguide is about 0.4 dB/cm at the 1550-nm wavelength. The on-chip insertion loss ranges from 5.5 to 11 dB and the crosstalk is less than -27 dB. The AWG router shows good cyclic rotation property of the wavelength channels with an error smaller than 0.03 nm [ABSTRACT FROM PUBLISHER]

We present a detailed experimental and theoretical study, showing that a novel nonzero dispersion-shifted fiber with negative dispersion enhances the capabilities of metropolitan area optical systems, while at the same time, reducing the system cost by eliminating the need of dispersion compensation. The performance of this dispersion-optimized fiber was studied using different types of optical transmitters for both 1310- and 1550-nm wavelength windows and for both 2.5-and 10-Gb/s bit rates. It is shown that this new fiber extends the nonregenerated distance up to 300 km when directly modulated distributed feedback (DFB) laser transmitters at 2.5 Gb/s are used. The negative dispersion characteristics of the fiber also enhance the transmission performance in metropolitan area networks with transmitters that use electroabsorption (EA) modulator integrated distributed feedback (DFB) lasers, which are biased for positive chirp. In the case of 10 Gb/s, externally modulated signals (using either EA-DFBs or external modulated lasers using Mach-Zehnder modulators), we predict that the maximum reach that can be accomplished without dispersion compensation is more than 200 km for both 100- and 200-GHz channel spacing. To our knowledge, this is the first demonstration of the capabilities of a nonzero dispersion-shifted fiber with negative dispersion for metropolitan applications [ABSTRACT FROM PUBLISHER]

We report on the integration of the Bragg filters with 1×8 multimode interference (MMI) power splitters on silicon substrate, and the demonstration of 1×8 external cavity distributed Bragg reflector (DBR) lasers. Hybrid organic-inorganic material is developed based on the sol-gel synthesis of an organically modified silicon alkoxide. The sol-gel material is spin coated on grating SiO2-Si wafers, and the designed components (splitters and filters) are UV imprinted and developed using solvent assisted photolithography. The Bragg reflectors show filtering up to 98% with a bandwidth of about 0.8 nm consistent with their theoretical prediction. Integrated reflectors and MMI splitters are then used as feedback resonators for DBR lasers. Single-mode lasing with sidemode suppressions of up to 40 dB and a linewidth of about 400 kHz is observed. At 1550- nm wavelength, the loss and power uniformity in the MMI splitters, designed on the basis of lowest loss, are, respectively, 0.13 dB and 0.03 dB poorer than their theoretical calculations [ABSTRACT FROM PUBLISHER]

A numerical design method for wavelength division multiplexing (WDM) transmission systems employing distributed Raman amplification (DRA) is proposed. This method evaluates fiber nonlinear effects by considering the equivalent fiber loss with DRA. The method is used to evaluate the performance of WDM transmission systems in which DRA is employed in a 1.55-μm dispersion-shifted fiber (DSF) transmission line. Transmission limit and the optimum fiber input powers for 1550-nm band (C-band) and 1580-nm band (L-band) transmission are investigated. Results show that bidirectional pumping is the best approach to extending transmission distance. Furthermore, the transport limits of optical transport networks that use DRA and optical add/drop multiplexers are analyzed [ABSTRACT FROM PUBLISHER]

A field-profile transformer utilizing a graded-index (GI) fiber having an oval core is proposed. Numerical investigation has demonstrated that the new fiber is capable of performing the profile transformation from elliptical fields that have high aspect ratios of up to 9, to circular fields, and vice versa. Experimental verification is also performed at a wavelength of 1550 nm, by making use of plastic GI fibers, demonstrating that a circular modal field of a standard single-mode fiber can be transformed into an elliptical field with an aspect ratio of 4.1. The transformer shows promise for low-loss coupling between fibers and functional devices that have elliptical fields, such as planar waveguides, semiconductor optical amplifiers, and laser diodes [ABSTRACT FROM PUBLISHER]

We compare the output spectra and data streams of a conventional 1550-nm semiconductor optical amplifier (SOA) with its gain-clamped (GCSOA) counterpart, in order to assess the impact of gain clamping on cross-gain modulation (XGM) and difference frequency generation (DFG). Whereas the conventional SOA exhibits a large amount of crosstalk due to XGM, there is virtually no XGM present in the GCSOA. However, the XGM effect in the SOA shows evidence of diminished efficiency at moderate input levels. We observe much higher DFG levels from the GCSOA (roughly 10 dB greater than the SOA). These DFG levels are such that cascaded wavelength cross-connect devices, in-line amplifiers, and even optical gates could experience inhibited performance [ABSTRACT FROM PUBLISHER]

We report on advances in polymeric waveguide technologies developed worldwide for the telecom and datacom markets, and we describe in detail one such technology developed at AlliedSignal. Optical polymers are versatile materials that can be readily formed into planar single-mode, multimode, and microoptical waveguide structures ranging in dimensions from under a micrometer to several hundred micrometers. These materials can be thermoplastics, thermosets, or photopolymers, and the starting formulations are typically either polymers or oligomers in solution or liquid monomers. Transmission losses in polymers can be minimized, typically by halogenation, with state-of-the-art loss values being about 0.01 dB/cm at 840 nm and about 0.1 dB/cm at 1550 nm. A number of polymers have been shown to exhibit excellent environmental stability and have demonstrated capability in a variety of demanding applications. Waveguides can be formed by direct photolithography, reactive ion etching, laser ablation, molding, or embossing. Well-developed adhesion schemes permit the use of polymers on a wide range of rigid and flexible substrates. Integrated optical devices fabricated to date include numerous passive and active elements that achieve a variety of coupling, routing, filtering, and switching functions [ABSTRACT FROM PUBLISHER]

In millimeter-wave (mm-wave) optical double sideband (DSB) signal transmission systems, the received radio frequency (RF) power fades periodically because of the group velocity dispersion (GVD) and the self-phase modulation (SPM) of optical fibers. In this paper, cancellation of the signal fading by using midway optical phase conjugation in mm-wave subcarrier multiplexed (SCM) optical DSB signal is analyzed. Fading-free 60 GHz mm-wave optical DSB signal transmission over 100 km-long nondispersion shifted single-mode fiber at 1550 nm by using a semiconductor optical amplifier (SOA) optical phase conjugator (OPC) in the midway of optical link is experimentally demonstrated for the first time. Finally, the degradation factor of the OPC system is also discussed [ABSTRACT FROM PUBLISHER]

Polybinary, optical amplitude modulated phase shift keying (AM-PSK) polybinary, M-ary amplitude shift keying (ASK), and polyquaternary signaling schemes operating at 10 Gb/s are investigated in 1550-nm lightwave systems operating over standard, single-mode fiber. The premise for exploring these signal types is that they concentrate power at frequencies closer to the optical carrier where phase distortion of the optical field from chromatic dispersion is less severe. Issues such as modulator chirp, optimal level spacing in a 4-ary ASK signal, and phase modulated to amplitude modulated (PM-AM) noise conversion from a nonzero laser linewidth are studied. It is found that higher order polybinary signals do not offer an improvement in dispersion tolerance over a duobinary signal. 4-ary ASK is demonstrated to increase the dispersion-limited distance to 225 km experimentally and 350 km through simulation, but at the expense of a ~8 dB degradation in receiver sensitivity due to the increased number of levels and the signal dependence of signal-spontaneous beat noise. Furthermore, the linewidth requirement for a 4-ary ASK signal is less than 1 MHz in order to minimize the impact of PM-AM relative intensity noise (RIN) when transmitting over 200-300 km [ABSTRACT FROM PUBLISHER]

We describe the design and operation of a 1550-nm diode pumped Er,Yb:glass laser with >130 mW of output power and a free running linewidth of ~22 kHz. Due to the low frequency relaxation oscillation, near shot limited relative intensity noise performance is obtained throughout the radio frequency (RF) range of interest for cable television and dense wavelength division multiplexed (CATV/DWDM) applications. For long-haul spans an intracavity lithium niobate phase modulator allows for chirping of the linewidth to bandwidths and at rates sufficient to defeat stimulated Brillouin scattering (SBS). For certain applications, the high output power can eliminate the need for an erbium-doped fiber amplifier (EDFA) [ABSTRACT FROM PUBLISHER]

Crosstalk in a two-wavelength 1550-nm standard fiber system at subcarrier frequencies 50-800 MHz is investigated. The dependence of the crosstalk on subcarrier frequency, wavelength spacing, and optical power is measured and analyzed. The observed crosstalk is attributed to three primary mechanisms: stimulated Raman scattering, cross-phase modulation, and the optical Kerr effect combined with polarization-dependent loss. At wavelength spacing greater than 9 nm, stimulated Raman scattering dominates. At wavelength spacing less than 5 nm, the primary contributor can be the optical Kerr effect with polarization dependent loss, except at higher modulation frequencies where cross-phase modulation also is significant. At even modest (by CATV standards) optical power, the crosstalk is as high as -40 to -45 dB [ABSTRACT FROM PUBLISHER]

A two-dimensional (2-D) wavelength division demultiplexing (WDDM) device is demonstrated to separate and to distribute multiwavelength optical signals by employing substrate-guided wave optical interconnects. Working principle and power budget issues are analyzed. In this planarized architecture, stacked/multiplexed input holographic gratings and arrays of output holographic gratings are designed to be fabricated on the same waveguiding plate to steer multiwavelength optical signals into different routing directions, to zigzag within a waveguiding substrate, and then to be surface-normally coupled out of the substrate. A dual-wavelength routing and distribution network is demonstrated in experiment at 780 nm and 790 nm. The crosstalk is measured to be >-30 dB. The fan-out energy fluctuation is within ±10% for each wavelength. We also demonstrate a planar three wavelength optical network to separate and distribute three wavelengths at 760, 790, and 820 nm. It is feasible for this structure to be used as high capacity wavelength division demultiplexing and routing networks at center wavelengths of 800, 1330, and 1550 nm [ABSTRACT FROM PUBLISHER]

The Raman time constant (TR) used in the generalized nonlinear Schrodinger equation is determined experimentally at 1550 nm based on the Raman self-frequency shift in a standard single-mode fiber. The effective value of the TR as measured is found to be 3.0 fs. Detailed error analysis shows that the uncertainty in the measurement is less than ±1.0 fs. The measured value of the TR is approximately half of what is commonly used at present in theoretical simulations. Determined experimentally in this work the accurate value of TR=3.0 fs is essential in modeling pulse propagation in optical fibers [ABSTRACT FROM PUBLISHER]

We present a tunable add-drop filter for wavelength division multiplexing (WDM) networks based on the resonant coupler (RC) principle. The device operates in the 1550-nm window with a wavelength spacing of 1.6 nm (200 GHz) and a periodicity of 6.4 nm (800 GHz). The splitting of the add and drop functions in an add-after-drop configuration results in extremely low homowavelength crosstalk and allows the individual design of the add and drop subfunctions to be optimized. The design of the flat-passband drop function is presented in detail. The compact filter is realized in high-index-contrast silicon-oxynitride technology, which permits small bending radii of 1.5 mm. Phase errors in the delay lines of the RC devices are compensated using the thermooptic effect, which is also used to tune the device. Measurement results on packaged devices show fiber-to-fiber losses of between 5 and 7 dB. The isolation of the transit WDM channels to the drop port is greater than 27 dB, and the rejection of the drop channel is 33 dB. The components are polarization insensitive and have been integrated in an add-drop WDM subsystem [ABSTRACT FROM PUBLISHER]

A compact and low-cost device that emulates a standard and dispersion-shifted 100-km single-mode fiber-optic link at 1550 nm is proposed. The device, composed of a chirped fiber grating and a monitor coupler, is analyzed by simulation and experimentally proved. A chirped fiber grating synthesis procedure and an explanation for both cases are also introduced [ABSTRACT FROM PUBLISHER]

A single-mode fiber connectorized microelectromechanical systems (MEMS) reflective optical switch attenuator operating in the 1550-nm wavelength region is described. The device consists of an electrostatically actuated gold-coated silicon vane interposed in a fiber gap yielding 0.81-dB minimum insertion loss in the transmit state and high transmission isolation in the reflection state with 2.15-dB minimum return loss. The switch attenuators also work as continuously variable optical attenuators capable of greater than 50-dB dynamic range and can be accurately regulated with a simple feedback control circuit. Switching voltages were in the range of 5-40 V and a switching time of 64 μs was achieved. The MEMS switch can be used in optical subsystems within a wavelength-division-multiplexed (WDM) optical network such as optical power regulators, crossconnects, and add/drop multiplexers. We used a discrete array of 16 switch attenuators to implement a reconfigurable 16-channel 100-GHz spacing WDM drop module of an add/drop multiplexer. Thru-channel extinction was greater than 40 dB and average insertion loss was 21 dB. Both drop-and-transmit of multiple channels (11-18-dB contrast, 14-19-dB insertion loss) and drop-and-detect of single channels (>20-dB adjacent channel rejection, 10-14-dB insertion loss) were demonstrated [ABSTRACT FROM PUBLISHER]

We have proposed and experimentally demonstrated a 10-Gb/s optically controlled buffer using a photonic-crystal-fiber (PCF)-based nonlinear optical loop mirror for all-optical packet-switched networks. The 10-Gb/s data can be stored in the buffer up to a period of 2.5 mus. By using the cross-phase modulation property between the control signal and the data signal inside the PCF, the total length of the fiber used in the buffer can be shortened to 30.9 m. The stored data packets are retrieved after they are stored in the memory for 2,4,..., and 12 round-trips. Independent bit-error-rate (BER) measurements have been carried out. The maximum power penalty is 3.3 dB at 1550 nm. The proposed buffer is wavelength transparent. For data packets stored in the C-band, the maximum power penalty after the data are stored in the memory for 12 round-trips is 3.5 dB at the BER of 10-9 [ABSTRACT FROM PUBLISHER]

A low insertion loss waveguide is fabricated in z-cut lithium niobate using femtosecond laser waveguide inscription. To fabricate a waveguide exhibiting both low propagation and coupling losses, we used the multiscan fabrication technique to control the size of the waveguide cross section. A minimum insertion loss of only 3.5 dB at 1550 nm was measured for the 18-mm-long waveguide when directly coupled to Corning SMF-28 fibers. Of this 3.5dB, we attribute 2.1 dB to coupling losses, 1.1 dB to propagation losses, and 0.3 dB to Fresnel reflections [ABSTRACT FROM PUBLISHER]

A single shallow ridge electroabsorption modulator monolithically integrated with a buried-ridge-stripe dual-core spot-size converter at the input and output port was fabricated by combining quantum-well intermixing and dual-core integration techniques simultaneously, using only a two-step low-pressure metal-organic vapor phase epitaxial process, conventional photolithography, and a chemical wet etching process. The optical insertion loss of the modulator in the on-state and the dc extinction ratio between 0 and -3 V at 1550 nm was -7.5 and 16 dB, respectively. The 3-dB modulation bandwidth was more than 10.0GHz in electrical-optical response [ABSTRACT FROM PUBLISHER]

We present the fabrication of a polarizing, endlessly single-mode microstructured fiber with high polarization-dependent loss. The fiber was fabricated by the stack-and-draw method. The resulting structure consists of a pure silica core surrounded by a regular lattice of air holes, in which four air holes in the inner ring have been enlarged. An extinction ratio of 16 dB/m with a transmission loss of 0.9 dB/m was achieved at a wavelength of 1550 nm [ABSTRACT FROM PUBLISHER]

Submicrometer silicon photodiode waveguides, fabricated on silicon-on-insulator substrates, have photoresponse from <1270 to 1740 nm (0.8 AW-1 at 1550 nm) and a 3-dB bandwidth of 10 to 20 GHz. The p-i-n photodiode waveguide consists of an intrinsic waveguide 500times250 nm where the optical mode is confined and two thin, 50-nm-thick, doped Si wings that extend 5 mum out from either side of the waveguide. The Si wings, which are doped one p-type and the other n-type, make electric contact to the waveguide with minimal effect on the optical mode. The edges of the wings are metalized to increase electrical conductivity. Ion implantation of Si+ 1times10 13 cm-2 at 190 keV into the waveguide increases the optical absorption from 2-3 dBmiddotcm-1 to 200-100 dBmiddotcm-1 and causes the generation of a photocurrent when the waveguide is illuminated with subbandgap radiation. The diodes are not damaged by annealing to 450 degC for 15 s or 300 degC for 15 min. The photoresponse and thermal stability is believed due to an oxygen stabilized divacancy complex formed during ion implantation [ABSTRACT FROM PUBLISHER]

Demonstrated is a novel silicon carbide (SiC)-based wireless optical sensor for cryogenic temperatures. The proposed design uses two wavelength processing and free-space optical beam interrogation of a remoted single crystal SiC chip placed in the cryogenic vacuum chamber to enable wireless temperature measurement. Experimental temperature sensing using the proposed sensor is reported from near room temperature to 100 K with an estimated 0.2 K resolution. The sensor uses eye safe laser wavelengths at 1550 and 1540 nm to implement the signal processing to determine the temperature value [ABSTRACT FROM PUBLISHER]

In this letter, we theoretically investigate the potential for further improvement of the slot waveguide structure in silicon-on-insulator at a wavelength of 1550 nm. Waveguide thickness and width, as well as slot thickness are optimized with respect to the optical power confined in the slot region by taking into account the modal behavior of the structure. A single-mode criterion is defined as a function of the geometry parameters [ABSTRACT FROM PUBLISHER]