Single-mode Fiber Array Research Articles

Holographic method of cohering fiber tapped delay lines

We propose, analyze, and demonstrate the use of a holographic method for cohering the output of a fiber tapped delay line (FTDL) that enables the use of fiber-remote optical modulators in coherent optical processing systems. We perform a theoretical examination of the phase-cohering process and show experimental results for a radio frequency (RF) spectrum analyzer that uses a lens to spatially Fourier transform the output of a holographically phase-cohered FTDL providing 50 MHz resolution and bandwidths approaching 3 GHz. Substantial improvements in bandwidth should be achievable with better fiber length-trimming accuracy and improvements in resolution can be obtained with longer fiber delay lines. We also analyze and demonstrate the use of a parallel holographic technique that compensates for polarization state scrambling induced by propagation through an array of single-mode fibers. Both the phase-cohering holography and the polarization fluctuation compensation can operate on hundreds of fibers in parallel, enabling both coherent optical signal processing with FTDLs and coherent fiber remoting of optically modulated RF signals from antenna arrays.

Elimination of Self-Contamination in High-Density Low-Loss Single-Mode Fiber Array Connectors

We report quantitative measurements of self-contamination in conventional and modified multi-SMF mechanically transferable (MT) connector ferrules. The modifications enable connector wear, insertion loss (IL), and IL reproducibility that are essentially equivalent to conventional ceramic ferrule connectors.

Optical Engineering: Elimination of Self- Contamination in High- Density, Low-Loss, Single Mode Fiber Array Connectors

Optical Engineering: Elimination of Self- Contamination in High- Density, Low-Loss, Single Mode Fiber Array Connectors

High-precision characterization of single-mode optical fiber arrays

A precise method of measuring core center dispersion in single-mode fiber arrays is presented. This approach dispenses with the use of high-precision linear translation stages and is based on a direct comparison of the fiber core center position to a simple lithographically patterned template. Combining image recognition and efficient processing algorithm, the fiber-core center positions of fiber arrays can be determined with precision of order of 0.1 /spl mu/m, in both longitudinal and transversal directions. Complementary information about the position of fibers within v-grooves as well as bending of multifiber arrays can be also obtained.

A two-way optical interconnection network using a single mode fiber array

We present a dynamic free space interconnection network for single mode fibers. The architecture consists of a two-way imaging geometry involving only one single mode fiber array. Input and output fibers belong to the same fiber array. Programmable and fixed diffractive optical elements are used for beam steering and wavefront correction. We show that the network ensures favorable conditions for launching and allows for a high interconnection volume with minimal insertion losses at 2.5 Gb/s. The architecture is also adapted to the use of binary electrically addressed spatial light modulators.

Single-mode fiber optical crossbar routing switch with ferroelectric liquid-crystal–VLSI technology and free-space optics

We investigate a possible extension of the optically connected parallel machine crossbar system to telecommunication routing-switching systems. The critical issue concerns the realization of a free-space interconnection system between two single-mode fiber arrays in the case of a fully interconnected architecture, such as a crossbar system. In particular, we assess the throughput capability of such a system. This evaluation is based on both theoretical analysis and experimental results. We demonstrate that the number of channels is severely constrained by the limited numerical aperture of a single-mode fiber. Finally, we discuss some architectural alternatives and propose some technical recommendations for interconnecting single-mode fiber arrays in free space.

A lensed-fiber coupling scheme utilizing a graded-index fiber and a hemispherically ended coreless fiber tip

A new configuration of lensed fibers as the coupling between laser diodes and single-mode fibers is proposed. The lensed fiber consists of a hemispherically ended coreless-fiber and a quarter-pitch length of a graded-index fiber. Fabrication is quite simple and rapid. Basic characteristics of the new configuration, including long working distances and wide tolerances, are experimentally verified. The new configuration is suitable for integration-oriented coupling between arrayed laser diodes and an array of single-mode fibers.

A passive micromachined device for alignment of arrays of single-mode fibers for hermetic photonic packaging-the CLASP concept

A micro-machined fiber alignment device, called the capture and locking alignment spring positioner (CLASP) has been fabricated. It uses a nickel leaf spring to passively capture vertical arrays of single-mode fibers with /spl sim/2 /spl mu/m accuracy.

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.

Multichannel fiber ferrule for a stable laser-diode array module

We developed a multichannel fiber ferrule for a stable laser-diode array module. To apply YAG laser welding to parallel butt couple between the laser-diode and the single-mode fiber arrays, hermetically sealed and precisely aligned equi-interval fibers are required. We describe a V-grooved ceramic ferrule for embedding fibers. Fibers are fixed by soldering, using a flat ceramic lid and aligned with a 250 μm pitch. Our ferrule allowed a metallic, stem mounting laser-diode, to be fixed by YAG laser welding. All 30 samples tested have a leak rate of less than 1×10/sup -10/ atm/spl middot/cc/s. Optical coupling of fabricated modules was 9.7/spl plusmn/0.2 dB and coupling loss change from 25/spl deg/C to 115/spl deg/C was within 0.5 dB.

A fiber lens with a long working distance for integrated coupling between laser diodes and single-mode fibers

A new scheme is proposed for lensed fibers with a long working distance, as used in the coupling between laser diodes and single-mode fibers. The scheme consists of the combination of a hemispherically-ended coreless-fiber tip and an expanded-core fiber. The working distance is measured as 169 /spl mu/m with a relatively low coupling-loss of 4.2 dB at a wavelength of 1.49 /spl mu/m. Tolerances for a 1-dB loss increment for axial-, lateral-, and angular-misalignment are 35, 2.6 /spl mu/m, and 0.8 degrees, respectively. The new configuration is suitable for alignment-free coupling between arrayed laser diodes and an array of single-mode fibers. >

200-Mb/s/ch 100-m optical subsystem interconnections using 8-channel 1.3-μm laser diode arrays and single-mode fiber arrays

Synchronous parallel optical-fiber transmission is an attractive method for providing increased interconnection throughput and higher density in advanced information systems. Skew suppression (reducing transmission delay time variation), error-free fully DC-coupled data transmission capability, compactness, and low power consumption of modules are important requirements. In order to meet these requirements, we developed optical subsystem interconnections using long-wavelength laser diode arrays and single-mode fiber arrays. The major design criteria are discussed, especially as they are related to skew due to laser diode turn-on delay and receiver input optical power variation. The use of low-threshold-current laser diode arrays is an important design requirement. Based on the design criteria discussed in this work, we demonstrated and channel 200-Mb/s/ch 100-m transmission using compact (0.18 cc/ch/module), low power (total 280 mW/ch), fully integrated transmitter and receiver modules with an ECL (emitter coupled logic) interface. These modules include our new laser diode arrays with low threshold current of 3.2 mA. Performance results showed that these modules are very effective as interconnections between synchronously operating subsystems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Highly efficient coupling between LD array and optical fiber array using Si microlens array

By using a Si microlens array, highly efficient coupling is realized between laser diode (LD) and optical-fiber arrays. The Si microlens is fabricated by transferring the lens shape of photoresist onto the Si surface using an etching process. For an optimal coupling scheme, a high-NA microlens with a diameter of 240 mu m and focal length of 190 mu m is designed and fabricated. The optical coupling efficiency for a four-channel system is -4.8+or-0.3 dB between an LD array with lasing wavelength of 1.55 mu m and a single-mode fiber array, which is the best data reported so far. Optical crosstalk exceeds -70 dB at the 250- mu m distant neighbor channel. >

Connectorized integrated star couplers on silicon

A connectorized integrated <i>N</i> x <i>N</i> passive star coupler suitable for use in single-mode multichannel optical networks is reported. The excess loss for most of the channels of the coupler is within 1.5 dB, with a worst value of 3 dB, of the unconnectorized coupling values, which range from 14.5 to 17.5 dB. The optical fibers are attached to the 19 x 19 coupler by butt-coupling a linear array of single-mode fibers using silicon v-grooves. Alignment is rapidly achieved with a compact six-degrees-of-freedom piezo-controlled micromanipulator. Best values of less than 0.1 dB per fiber attachment, dependent on connector quality, were obtained. The coupler demonstrated negligible reflection effects when used as the central element in a 1-Gb/s frequency-division-multiplex network experiment.

Permanent attachment of single-mode fiber arrays to waveguides

We report on coupling arrays of SM fibers in silicon V - grooves to waveguides. Arrays with up to 12 fibers have been permanently attached to waveguides with an average excess loss of 0.3 dB per interface. We discuss a subtle, heretofore unreported effect of polarization on fiber-waveguide insertion loss and we describe the first measurements of waveguide-mode position as a function of polarization. In general, the modes of a Ti:LiNbO 3 waveguide peak at different positions. This results in different optimum positions for coupling and thus leads to an unavoidable excess loss when attaching fibers. For low-loss waveguides, we predict a minimum excess loss of 0.25 dB per interface.