C.R. Giles

Simultaneous wavelength-stabilization of 980-nm pump lasers

High power 980-nm strained QW semiconductor lasers connected to the input ports of a 4/spl times/4-fused fiber star coupler are simultaneously wavelength-locked through reflection from a single narrow-band fiber grating connected to one output port. This configuration enables simple pump wavelength control, inhibits deleterious pump-laser interactions, and improves amplifier reliability through pump redundancy.<<ETX>>

Access PON using downstream 1550-nm WDM routing and upstream 1300-nm SCMA combining through a fiber-grating router

We describe an 8-channel access passive optical network using a fiber grating router at the remote node, 50 Mb/s 1550-nm WDM downstream transmission from an integrated multifrequency laser, and 3 Mb/s 1300 nm SCMA upstream transmission. This approach combines the advantages of a downstream WDM PON and an upstream low-cost power-combining PON.

Asymmetric fiber microlenses for efficient coupling to elliptical laser beams

It is demonstrated that it is possible to fabricate asymmetric hyperbolic microlenses directly on the ends of single-mode optical fiber to enhance the fibers coupling to elliptical laser beams. The lenses, with controlled eccentricity ratios, are made by micromachining the end of the fiber with a pulsed CO/sub 2/ laser, as the fiber is directed by computer control about the focussed laser beam. Coupling efficiencies of 84% (-0.74 dB) have been realized with single transverse mode lasers at a wavelength of 0.98 mu m having an approximately 3 to 1 beam ellipticity. With multitransverse-mode lasers at 1.48 mu m having similar ellipticities, the asymmetric lenses demonstrate a 2-dB increase in coupling efficiency over symmetric hyperbolic microlenses. The authors have coupled about 120 mW from such a 360 mW laser, used to pump erbium-doped fiber amplifiers, into single-mode fiber.<<ETX>>

All-optical XOR and XNOR operations at 86.4 Gb/s using a pair of semiconductor optical amplifier Mach-Zehnder interferometers

We propose a method for increased-speed all-optical XOR operation using semiconductor optical amplifiers. We demonstrate XOR and XNOR operations at 86.4 Gb/s using a pair of photonic-integrated semiconductor optical amplifier Mach-Zehnder interferometers.

2.5 and 10 Gb/s transmission experiments using a 137 photon/bit erbium-fiber preamplifier receiver

An optical-preamplifier receiver with sensitivity of 137 photons/bit at 2.5 Gb/s and 1.530- mu m wavelength is presented. The sensitivity is 193 photons/bit at 10 Gb/s. The authors discuss the degradations from the quantum-limited value of 38 photons/bit. By employing an optical power amplifier at the transmitter, the authors demonstrate 2.5 Gb/s-250 km and 10 Gb/s-220 km transmission through dispersion-shifted fiber.<<ETX>>

An erbium-doped multimode optical fiber amplifier

The authors describe the first experimental study of an erbium-doped multimode fiber amplifier. The focus has been to characterize an intermediate core erbium-doped optical fiber, a fiber that is capable of propagating many guided modes at both the signal and pump wavelengths, and to determine the feasibility of using such an active fiber as a multimode fiber amplifier, by measuring its gain, noise, and pump power requirements. For a 2-m length of a 13- mu m-core erbium-doped fiber, the authors measured gain as high as 16 dB at a signal wavelength of 1543 nm, with approximately 100 mW pump power (980 nm). For these same test conditions, the smallest excess noise factor beta was 42.<<ETX>>

Reflection-induced changes in the optical spectra of 980-nm QW lasers

High-power 980-nm strained quantum well diode lasers having low reflectivity facet coatings are sensitive to weak reflections that affect the laser emission spectrum. In devices having 0.2% output facet reflectivity, 2% reflections from an external plane mirror shifted the output spectrum from 970 to 1000 mn. Wavelength stabilization and improved immunity to spurious reflections were demonstrated using bulk grating and fiber-grating reflectors. Continuous laser tuning from 958 to 1011 nm was achieved with 1% net grating reflectivity.<<ETX>>

Amplified integrated star couplers with zero loss

It is shown that it is possible to compensate for the approximately 17 dB splitting and excess loss of a 19*19 integrated star coupler with erbium-doped fibers (EDFs) connected to the output channels. The amplifier fibers are pumped to near-quantum-limited noise performance using only one laser source at 0.98 mu m, which is connected to one of the input ports and is distributed to the EDFs through the star itself. The integrated star couplers near-wavelength-independent performance is able to transmit both the pump light at 0.98 mu m and the signal at 1.55 mu m with a loss differential on the order of only 1 dB.<<ETX>>

Demonstration of broad-band PMD mitigation in the presence of PDL through distributed fast polarization scrambling and forward-error correction

We experimentally demonstrate broad-band mitigation of polarization-mode dispersion (PMD) in the presence of polarization-dependent loss (PDL) by using distributed fast polarization scramblers in systems adopting forward-error correction. The combined penalty of PMD and PDL is smaller than the sum of the individual penalties, which shows the robustness of the PMD mitigation scheme against PDL and the enhancement of PMD tolerance improvement in the presence of PDL. The desired number of scramblers and their distribution are also discussed.

Polarization-independent phase conjugation in a reflective optical mixer

A reflective optical mixer based on four-photon mixing is used to generate a phase conjugate copy of an input optical signal of arbitrary polarization. For some polarization states of the pump and signal, the phase conjugate signal is polarization-scrambled. Measurements at 1.8 Gb/s confirm the potential use of the reflective optical mixer in lightwave systems.<<ETX>>