Fiber Pigtail Research Articles

Compact and low-loss arrayed waveguide grating module with tolerance-relaxed spot-size converter

A compact, low-loss arrayed waveguide grating (AWG) module was achieved by adopting a novel optical spot-size converter (SSC) to planar lightwave circuits (PLCs). The SSC is a laterally tapered waveguide that can be fabricated simply by the conventional fabrication process. The structure is composed of a core width converting region where the spot-size is converted efficiently, and a core width fine-tuning region where the cut-position tolerance is relaxed. We have applied this structure to a 1.5%-/spl Delta/ silica-based waveguides and reduced the single-mode fiber coupling loss to less than 0.5 dB/point. The SSC provides a large cut-position tolerance that enables angle polishing of the PLC endfaces to prevent reflection and low-loss connection of pigtail fibers. The center channel insertion loss of the AWG module was reduced from 4.2 to 2.2 dB, and the reflection was less than -60 dB.

Vertical Cavity Light Emitters for Plastic Optical Fibers

Plastic optical fibres, which have a local attenuation minimum at 650 nm, have attracted much interest for low-cost short-haul communication systems. Red vertical-cavity surface-emitting lasers (VCSELs) and resonant cavity light emitting diodes (RCLEDs) provide a potential solution as light sources for these systems. The operation principle of vertical cavity emitters is based on a Fabry-Perot microcavity, which is formed by placing an optically active region inside of two parallel mirrors. The RCLEDs with emission windows of 84 μm in diameter, suitable for standard POFs, exhibit bandwidths up to 200 MHz and light power of 3 mW (cw). The maximum external quantum efficiency is 9.5%. Larger devices, ø500 μm in size, launch light power up to 15 mW. Record high transmission rates, 622 Mbit/s, with bit-error-rate <1 × 10-11 have been demonstrated for a 1-m-long step-index POF. Neither sudden unexpected failure, nor gradual power degradation has been observed after operation under accelerated ageing conditions for about 100 000 device-hours. The alignment tolerance of the coupling efficiency is found to be very large, ±0.5 mm in all directions x-y-z, suggesting that the fibre pigtail packaging is inexpensive. First MBE-grown visible AlGaInP vertical-cavity surface-emitting lasers have been demonstrated. A laser with a 10-μm emitting window has external quantum efficiency of 6.65% under continuous wave operation and it is still lasing at 45°C. Furthermore, a threshold current less than 1.0 mA is obtained for a device, which has an 8-μm emitting window.

A compact 3R-receiver module for short-haul SDH STM-16 systems

This paper describes a complete 3R optical receiver module for synchronous digital hierarchy (SDH) STM-16 short-haul systems, housed in a 20-pin dual-in-line (DIL) ceramic package. The module includes an InGaAs p-i-n photodiode, a commercial GaAs transimpedance amplifier, and a custom-made silicon bipolar frequency- and phase-locked loop (FPLL)-based clock and data recovery (CDR) circuit. The fiber pigtail is actively aligned to the photodiode by using a proprietary technology that uses a silicon-based optical submount assembly (OSA). The use of a clock recovery circuit based on an FPLL allows avoiding an external low-frequency reference clock and achieving a root-mean square (rms) jitter of 0.075 UI. The module requires two supply voltages of 5 V and -4.5 V, for a total power dissipation of 930 mW, and has a total volume below 0.75 cm/sup 3/ (24.7/spl times/9.9/spl times/3 mm/sup 3/). Measurements have shown full compatibility with SDH standards.

Post-weld-shift in dual-in-line laser package

The post-weld-shift (PWS) effect in laser welding for a dual-in-line package (DIP) with fiber pigtail to semiconductor laser connection has been studied experimentally and numerically. Experimental results show that the PWS of an optical component welded by a dual-beam laser system deforms and the welded component rotates counterclockwise as the difference of the energies between two laser beams increases. This indicates that the PWS in laser packaging can be minimized by properly controlling the laser beam-to-beam energy balance. A thermal-plasticity coupled finite-element model (FEM) has been also carried out on the analysis of the effect of PWS in laser packaging. Numerical results show that a PWS in the DIP may be introduced from an unbalanced distribution of residual stresses introduced from the solidification shrinkage. A satisfactory agreement between the experimental results and FEM calculations suggests that the FEM may provide an effective method for predicting the PWS in laser welding technique for optoelectronic packaging.

Fiber ribbon alignment structures based on rhombus-shaped channels in silicon

A fiber ribbon alignment structure based on bulk silicon micromachining technique with precise rhombus-shaped channels in {100}-silicon is demonstrated. The main advantages are totally buried and thereby protected fibers and a less structured wafer surface suitable for the integration of components on top. The presented structure allows a simplified assembly of fiber ribbon arrays due to integrated funnels for fiber insertion. The accuracy of the channels within an array was found to be /spl plusmn/0.2 /spl mu/m. Furthermore, this technique allows combining fiber ribbons with a pitch of 250 /spl mu/m with photodiodes for system monitoring in a single fiber pigtail.

Remote opto-chemical sensing with extreme sensitivity: design, fabrication and performance of a pigtailed integrated optical phase-modulated Mach–Zehnder interferometer system

This paper describes the design, fabrication and testing of a pigtailed integrated optical (IO) phase-modulated Mach–Zehnder interferometer (MZI) including both the optical chip and the electronics. The optical chip is realised in SiON technology. The IO components (the sensing function, the straight waveguiding channels, the phase modulator, the polariser, the splitter, the combiner and the fibre-to-chip connection unit) are individually optimised and interconnected by using transversal adiabatic tapers. To obtain a high waveguide evanescent field sensitivity, the sensor is designed for — but not limited to — a wavelength of 632.8 nm. The integrated MZI is actively phase-modulated by virtue of the electro-optic effect of the incorporated material zinc oxide (ZnO). The electro-optical voltage–length product V π is ∼16 V cm at frequencies above ∼10 Hz. The polariser is a distributed function, that effectively filters TM-polarised light (TE/TM polarising ratio >30 dB). The fibre pigtail, affording remote optical sensing, is based on a cheap, easy-to-use fibre-to-chip connection with a typical coupling efficiency of 50%, while the device throughput (“insertion loss”) is ∼−20 dB. The drive- and demodulation electronics enable a phase resolution 5×10 −5×2 π, corresponding to a refractive index resolution of ∼2×10 −8. The sensing system as has been realised up to now shows a phase resolution of ∼1×10 −4×2 π, its long-term stability (hours) being ≤3×10 −4×2 π. This corresponds to a refractive index resolution of ∼5×10 −8, and a long-term stability of ∼10 −7.

High-speed digital Y-branch switch/modulator withintegrated passive tapers for fibre pigtailing

A 1 × 2 digital optical switch in InGaAsP multiple-quantum-wells with an 8 GHz bandwidth is demonstrated, which may also be operated as a wavelength-, polarisation-, and drive-voltage insensitive modulator. The total length of the switch/modulator device is 3 mm which includes passive fan-outs for fibre interconnection. The on-chip insertion loss is 3 dB out of which the Y-branch excess loss is only 0.7 dB. The measured switch crosstalk is –18 dB for a 4 V push-pull bias. Further crosstalk reduction is expected from a more optimised design and improved fabrication processes.

Underwater Acoustic Sensor Using Optical Fiber Bragg Grating as Detecting Element

An underwater acoustic sensor using an optical fiber Bragg grating (FBG) in the reflection mode is examined to characterize the sensor under various conditions. For the fabrication of the sensor, one end of the FBG fiber pigtail is terminated by a low reflection facet such as an APC connector or an angled cut fiber and the output signal is extracted by an optical circulator of low back reflection. The sensor demonstrated as good performance of fundamental characteristics as a FBG acoustic sensor in the transmission mode. Considering many of the basic properties such as sensitivity, linearity, frequency response and compactness, an acoustic sensor using a FBG is as good as or better than a conventional PZT acoustic sensor.

Fabrication of alignment grooves in LiNbO 3 substrates for simplified optical fibre pigtailing

A technique for fabricating alignment grooves in LiNbO3 substrates, for simplified optical fibre attachment, is reported. The grooves are produced through the etching of material that has been domain inverted via spatially selective electric field poling. The etched grooves are of very high surface quality, and have a profile that is determined by the area of domain inversion produced. The technique lends itself to a method of fibre alignment that is simplified, more reliable, and less labour intensive than existing schemes.

A simple passive-alignment packaging technique for laser diode modules

A simple passive-alignment packaging technique has been developed for the fabrication of a laser diode connection to a singlemode fiber pigtail. The fabrication begins with a multimode fiber soldered in a U-groove with 5 μm tolerance. Then the laser chip with a junction-up diebond is passively aligned to a multimode fiber and converted into a singlemode fiber. The tolerance as measured for the multimode fiber at 10% loss of maximum coupling from the laser diode is 11 μm. Because the tolerance of the multimode fiber from the laser chip is larger (11 μm) than that of the fiber in the U-groove (5 μm), this passive alignment is easily obtained. In contrast to other passive-alignment techniques, the advantages of this technique are that it is less sensitive to transverse misalignment and requires no complicated alignment marks. From laser to multimode fiber a coupling efficiency of greater than 80% and a bandwidth of greater than 1 GHz have been achieved. In this package, the overall coupling efficiency from laser to singlemode fiber is 16%. The resulting laser module with compact size and fewer components should make it highly suitable for use in low-cost telecommunication applications.

Reliability and Environmental Stability of Polymer based Solid State Optical Switches

The development of reliable and environmentally stable photonic space switches based on the BeamBoxáTM Solid State Optical Switch technology is described. The realization of a robust temperature stable (-40°C to 75°C) fiber pigtail attachment joint is presented.

PLC connector with fibre physical contact

A novel planar lightwave circuit (PLC) connector utilising physical contact (PC) between bare fibres and waveguides was developed. This connector allows the use of PLC-based optical modules without fibre pigtails. The fabricated connectors successfully realised average connection and return losses of 0.25 and 43 dB, respectively.

Simplified SC‐type receptacles for optical subscriber systems

We have developed novel, low-cost, simplified SC-type receptacles. They can be attached to the fiber pigtails of optical modules and are fully compatible with conventional SC plugs. We have developed three types of simplified receptacle: simplex and duplex types for use with an ONU module and an eight-port receptacle for a fiber termination module. They have the same optical characteristics as conventional SC connectors, such as a connection loss of 0.06 dB and a return loss of 50.6 dB, and exhibit no degradation during or after mechanical and environmental tests. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 2, 80(3): 39–46, 1997

Optical-mode transformer: a III-V circuit integration enabler

Further development in optical fiber communications at 1.3 and 1.5 /spl mu/m not only requires the improvement of components, but also hinges on the capability to fabricate optoelectronic circuits on a mass scale. Hybrid and monolithic integration of these components are expected to yield the means to mass produce optoelectronic circuits with the required characteristics. Effort is currently deployed to find simplified ways to optically interconnect such diverse components as lasers, modulators, waveguides, switches, filters and detectors, either by fiber pigtailing, hybridization on a Si-motherboard; or by monolithic integration on a single chip of InP. In this paper, emphasis is placed on the efficiency of optical-mode transformer (OMT) as a versatile solution to overcome the main technological obstacles of optical interconnection between InP-based components. A few examples will highlight the enabling qualities for fiber pigtailing and photonic integration.

Effects of Langmuir–Blodgett-film gas sensors with integrated optical interferometers

Novel Langmuir-Blodgett-film toxic-gas sensors that have a Ti:LiNbO(3) integrated optical Mach-Zehnder interferometer structure are experimentally investigated. The gas-sensing properties of the sensors are obtained for NO(2), Cl(2), NH(3) , and H(2)S by means of the detection of optical output changes. All the optical connections are made with optical fiber pigtails.

Ultrafast monolithically integrated InP-based photoreceiver: OEIC-design, fabrication, and system application

An InP-based photoreceiver OEIC for /spl lambda/=1.55 /spl mu/m with a bandwidth of 27 GHz is reported. The receiver design, fabrication and characterization is presented. The device consists of an optical waveguide-fed pin-photodiode and a coplanar traveling-wave amplifier being composed of four GaInAs-AlInAs-InP-HEMT's. The photodiode exhibits an external quantum efficiency of 30% and a 3-dB power bandwidth of 35 GHz. HEMT's with 0.7-/spl mu/m gate length, integrated on semi-insulating optical waveguide layers show cutoff frequencies f/sub T//f/sub max/ of 37/100 GHz at zero gate bias. Traveling-wave amplifiers with 0.5-/spl mu/m gate HEMT's have 28-GHz bandwidth. The receiver OEIC is packaged into a module with fiber pigtail and operates successfully within an SDH based 20-Gb/s transmission system. An overall system sensitivity of -30.5 dBm was achieved at a BER=10/sup -9/ after signal transmission over 198-km dispersion shifted fiber.

Photonic integrated transceiver for the access network

To reduce fabrication costs of fibre-optic terminal modules for interactive services, an InGaAsP/InP chip fabrication process has been developed for monolithic integration of a strained-layer multiple quantum well laser, a monitor diode and a photoreceiver with a 1300/1530nm filter. Reception responsivity and output power of the chips are 0.1 AW-1 at 1300nm wavelength and 4.5mW at 1530nm wavelength, respectively. At present, complete modules with fibre pigtail exhibit 0.7mW launch power, but 1.4 mW is expected with the latest chips.

Laser welding for fiber pigtailing with long-term stability and submicron accuracy

Laser welding as a means for optical packaging, providing long-term stability and submicron precision, has been implemented for fixing single-mode fibers or fiber arrays to integrated optical waveguides of GaAs and InP optoelectronic chips. Fixing accuracies better than 0.5 μm are achieved by applying a new method of corrective welding. Devices such as high-power LEDs featuring low spectral modulation, 980-nm laser diodes, integrated reflective Mach-Zehnder modulators (GaAs), and 1 x 2 InP switches have been packaged and used in system test beds.

Fabrication and transmission experiments of distributed feedback laser modules for 2.5 Gb s-1 optical transmission systems

A distributed feedback (DFB) laser module has been developed for 2.5 Gbs-1 optical transmission systems. The DFB laser has a multiple-quantum-well (MQW) active layer and a planar buried heterostructure (PBH) for a low threshold current and stable singlemode operation with low chirping. A PBH DFB laser module with a single-mode fibre pigtail and an optical isolator was designed and fabricated by employing a single lens and a laser welding method. The fabricated MQW PBH DFB laser module is shown to be a suitable light source for 2.5 Gb s-1 optical transmission systems with a minimum received power of-33 dBm after 47 km conventional optical fibre transmission.

First system experiments with a monolithically integrated tunable polarization diversity heterodyne receiver OEIC on InP

System performance of an integrated polarization diversity heterodyne receiver optoelectronic IC (OEIC) is reported. The OEIC is monolithically integrated on InP. It includes a tunable 4 section DBR laser (quasi continuous tuning range 3.5 nm) and balanced photodiodes. The packaged OEIC is supplied with a fiber pigtail. Stable and polarization independent operation is achieved without any tendency for a bit error floor. The sensitivity at 1550.2 nm is -33.5 dBm at a bitrate of 140 Mbit/s. The performance of the OEIC based receiver is verified by operating in an experimental OFDM-TV distribution system with 4 channels. >