Thomas Andrew Strasser

Grating resonances in air-silica microstructured optical fibers.

We report what is believed to be the first demonstration of optical fiber gratings written in photonic crystal fibers. The fiber consists of a germanium-doped photosensitive core surrounded by a hexagonal periodic air-hole lattice in a silica matrix. The spectra of these gratings allow for a detailed characterization of the fiber. In particular, the gratings facilitate coupling to higher-order leaky modes. We show that the spatial distribution and the effective index of these modes are determined largely by the design of the lattice and that the grating spectra are unaffected by the refractive index surrounding the fiber. We describe these measurements and corresponding simulations and discuss their implications for the understanding of such air-hole structures.

Electrically tunable power efficient dispersion compensating fiber Bragg grating

Novel devices only offer reasonable telecommunication solutions when they can be packaged and manufactured efficiently and at low cost. We demonstrate such a compact and power efficient tunable dispersion compensating fiber Bragg grating (FBG) device. The device relies on a distributed on-fiber thin-film heater deposited onto the outer surface of an unchirped FBG. Current flowing though the thin film generates resistive heating that is governed by the thickness profile of the metal film. A chirp in the grating is obtained by using a coating whose thickness varies with position along the length of the grating in a prescribed manner; the chirp rate is adjusted by varying the applied current. Using an electrical power of less than 1 W in a packaged device, we demonstrate a linearly chirped Bragg grating in which the dispersion is continuously tuned from -300 to -1350 ps/nm, with an average deviation from linearity of approximately 10 ps.

Fast-link control protection of surviving channels in multiwavelength optical networks

Link control, a new technique for protecting surviving channels on a per-link basis from fast power transients resulting from network reconfigurations or line failures, is demonstrated in a 560-km eight-amplifier wavelength division multiplexed link carrying seven 2.5-Gb/s channels plus the link control channel.

DISTRIBUTED ON-FIBER THIN FILM HEATERS FOR BRAGG GRATINGS WITH ADJUSTABLE CHIRP

This letter describes a fiber Bragg grating device that has tunable chirp. It relies on a distributed on-fiber resistive heater that consists of a thin metal film deposited onto the outer surface of a bare fiber; the thickness of this film varies continuously with position along the fiber. The physics of heat flow and diffusion in these structures leads to temperature gradients that follow, to a remarkably good approximation, the local resistance of the tapered metal film. This temperature distribution produces a chirp with a geometry that is defined by the thickness profile of the film and at a rate that can be adjusted by changing the current. Finite element modeling illuminates aspects of the flow of heat in these structures, and optical measurements demonstrate important characteristics of the devices.

3.28 Tb/s (82/spl times/40 Gb/s) transmission over 3/spl times/100 km nonzero-dispersion fiber using dual C- and L-band hybrid Raman/erbium doped inline amplifiers

We demonstrate transmission of a record aggregate capacity of 3.28 Tb/s (82/spl times/40 Gb/s PRBS 2/sup 31/-1 NRZ) over 3/spl times/100 km of a demonstration TrueWave(R) fiber with very low dispersion slope. The system for the first time incorporate dual C- and L-band transmission and distributed Raman amplification in addition to the 40 Gb/s line rate.

Dynamic post dispersion optimization at 40 Gb/s using a tunable fiber Bragg grating

A compact tunable fiber Bragg grating that uses distributed thin-film heaters on the surface of the fiber is used to dynamically optimize the post dispersion compensation of a multi-span 40-Gb/s nonreturn-to-zero (NRZ) transmission system. Dynamic post dispersion compensation with this device enables the system to operate over a much wider range of launch power than is otherwise possible with simple, fixed compensation using dispersion compensating fiber.

A gain-flattened ultra wide band EDFA for high capacity WDM optical communications systems

An 84 nm gain-flattened ultra wide band erbium-doped silica fiber amplifier for high capacity WDM optical communication systems is demonstrated with a noise figure of 6 dB and an output power of 25 dBm. We demonstrated an ultra wide band EDFA with a two-section, split band structure. The total 3dB bandwidth is 84.3 nm, which should be able to support 100 WDM channels with 100 GHz channel spacing or 200 WDM channels with 50 GHz channel spacing. The split bands allow independent optimization of each band for dispersion compensation and span loss variations.

Dual on-fiber thin-film heaters for fiber gratings with independently adjustable chirp and wavelength

Dual, independently addressable thin-film resistive heaters fabricated in a multilayer geometry on the surface of an optical fiber provide a new, flexible means for thermally tuning the properties of intracore gratings. In particular, control of the current that is applied to each of these heaters permits the chirp and the central wavelength of the grating to be adjusted independently. The designs and simple fabrication procedures for these types of device, the important physics of heat flow in them, and a tunable add-drop filter that demonstrates essential aspects of their operation are described.

Enhanced thermal and magnetic actuations for broad-range tuning of fiber Bragg grating–based reconfigurable add–drop devices

We demonstrate two new approaches to broad-range tuning of fiber Bragg grating devices: amplified thermal tuning and programmable magnetic tuning. The thermal-strain tuning approach employs a novel configuration to amplify thermally induced wavelength shifts by use of a negative thermal-expansion component. The magnetic-strain tuning approach allows programmable and latchable wavelength shifts through magnetic interactions that induce controlled strain on the fiber grating. The advantages and disadvantages of these two techniques are contrasted.

Electrically tunable power efficient dispersion compensating fiber Bragg gratings for dynamic operation in nonlinear lightwave systems

We demonstrate a power efficient (<0.5 W) tunable dispersion compensating fiber Bragg grating device and show for the first time dynamic optimization of dispersion in a nonlinear lightwave system. Operation is demonstrated in a 20 Gbit/s single channel NRZ system where the device was used to adjust the dispersion to the power-dependent optimal dispersion required for optimum performance.