Summary form only given. We present a two-stage, double-pass polarization-maintaining Er-doped fiber amplifier (PM-EDFA) with a high saturated output power (Psat) composed of reliable, commercially available components. The high output power is achieved by multiplexing four pump lasers together with polarization-insensitive dense WDM fused tapered couplers. The pump diode laser wavelengths ranged from 970-985 nm, with a 5-nm separation. At the recommended operating current, the nominal power of each pump before the WDM combiner was 90 mW and the output pump power from each set of four combined pump lasers was 330 mW.

We describe recent results of the Advanced Research Projects Agency (ARPA) sponsored Consortium on Wideband All-Optical Networks which is developing architectures, technology components, and applications for ultrafast 100 Gb/s time-division multiplexing (TDM) optical networks. The shared-media ultrafast networks we envision are appropriate for providing low-access-delay bandwidth on demand to both future high-burst rate (100 Gb/s) users as well aggregates of lower-rate users (i.e., a heterogeneous user population). To realize these goals we are developing ultrafast network architectures such as HLAN, described here, that operate well in high-latency environments and require only limited processing capability at the ultrafast bit rates. We also describe results on 80-Gb/s, 90-km soliton transmission, 100-Gb/s soliton compression laser source technology, picosecond short-pulse fiber ring lasers, picosecond-accuracy optical bit-phase sensing and clock recovery, all-optical injection-locked fiber figure-eight laser clock recovery, short-pulse fiber loop storage, and all-optical pulse width and wavelength conversion.

A novel geometry for all-optical clock recovery using a semiconductor amplifier yields a strong locking mechanism in a short cavity. The recovered clock has a large locking bandwidth, low timing jitter, and fast lock-up time at a 2.5 GHz rate. Preliminary results at a 9 GHz rate also indicate a high quality recovered clock.

All-optical timing extraction using a figure-eight laser with a semiconductor nonlinearity generates a synchronised 40GHz output pulse stream which displays lower timing jitter than the input stream. A high contrast ratio recovered clock is observed over a similar to 200kHz locking range.

High power erbium-doped fiber amplifiers have a number of applications, including broadcast sources for cable TV, long distance repeaterless links, nonlinear optical switching, laser radar, remote sensing, and medicine. Considerable progress has been made to develop high power sources.1,2,3 We have demonstrated a 3-stage optical amplifier with 2 watts of output power at 1.5 μm, which we believe to be the highest reported output power for an erbium amplifier directly pumped with semiconductor lasers.

High data rate communications systems will soon be needed for space applications. Technology and applications which support high data rates are already in place for ground- based telecommunications, or will be in the future. The advantages of an optical system over a traditional RF link for free space communications are particularly compelling for high data rates. We have been developing the necessary technology to demonstrate the feasibility of high rate free-space optical communications technology at 1.5 micrometers . The existence of a large, mature technology base at 1.5 micrometers developed for the telecommunications industry has allowed us to focus our development effort on two key technologies needed for space applications that have not been developed for the ground: a 1 Watt class optical power amplifier and a near quantum limited receiver. This paper will describe the overall system design for a high data rate optical communications system and present experimental results demonstrating < 50 photons/bit sensitivity at 10 Gbps with 1 Watt of optical power. The existence of a feasibility demonstration at this data rate enables downward scalability to data rates of 1 Gbps or less with small, inexpensive terminals.

High data rate communications are of interest for many applications. In fiber-based broadcast systems, high receiver sensitivity and high transmitter power translate into the ability to reach more customers. For space applications, high receiver sensitivity and high optical power are essential since it is impossible to use amplifiers between the transmitter and receiver. We describe here the experimental demonstration of a 10-Gbps communications system with a receiver sensitivity of 77 photons/bit at a bit error rate of 10/sup -9/ and a one-watt optical transmitter based on an erbium-doped fiber amplifier pumped by tapered-gain-region semiconductor lasers.<>

A novel geometry for all-optical clock recovery using a semiconductor amplifier yields a strong locking mechanism in a short cavity. The clock recovery laser is characterized with regard to its performance in a system environment. The clock circuit is operated at data rates from 1 to 40 GHz and exhibits a large locking bandwidth and low timing jitter.

An anamorphic microlens has been developed to couple a tapered unstable-resonator laser directly to a single-mode fiber, and has demonstrated capability for simple, compact and efficient high-power diode laser systems. Far high collection and coupling efficiencies, the refractive microlens has been fabricated by utilizing both sides of a GaP substrate, in which the first side was used to remove the astigmatism of the laser output and the second side to focus the beam to a spot size comparable to the fiber mode. The microlenses have been accurately formed by using a recent technique of mass-transport smoothing of etched multimesa preforms. Initial fiber-coupling experiments showed powers as high as 360 mW at the fiber output, and coupling efficiency as high as 29.5% has been measured at a lower power.< >

An important application of tapered gain region semiconductor lasers is as a pump source for erbium doped fiber amplifiers. We have been developing a 1 Watt-class erbium-doped transmitter amplifier for optical intersatellite communications. Previously, high power erbium-doped amplifiers have been demonstrated using erbium-ytterbium codoped fiber and Nd:YAG pumps, but this approach has a lower wall-plug efficiency than directly pumping at 980 nm. We will discuss recent high power EDFA results

A simple method for collimating the optical output of a tapered gain region amplifier or laser and coupling to a single-mode optical fiber is described, along with a technique for quantitatively assessing the expected coupling efficiency. By using a tapered laser, 840 mW at 980 nm was coupled into single-mode fiber with 44% efficiency measured from fiber input to available internal fiber power, in excellent agreement with the 48% predicted. When transmission losses of the collimating optics are included, the power coupling efficiency referred to the laser facet power is 32%.

A novel geometry for all-optical clock recovery is demonstrated using a semiconductor laser amplifier in a nonlinear optical loop mirror to modelock a figure eight laser. A clock signal can be recovered over a broad locking bandwidth of 0.5 MHz when random data at 1 Gbit/s are input to the system.<>

Semiconductor laser devices with tapered gain regions have recently generated much interest because they promise high output power with near-diffraction-limited spatial beam quality and good electrical to optical conversion efficiency. We report recent progress on two specific applications: a ring laser and a high- power erbium-doped fiber amplifier (EDFA). The ring laser operates unidirectionally in a single longitudinal mode with an output power of 170 mW and without a Faraday isolator. The high- power EDFA has an output power of 520 mW at 1.55 micrometers , the highest power reported to dates for an erbium-doped fiber amplifier using all semiconductor pump lasers. The common theme for both of these applications is the development of optical systems that produce high power in near-diffraction-limited collimated beams and efficient coupling into single mode optical fiber. We present an experimental procedure for quantitatively predicting the optical fiber power coupling efficiency. We have measured 64% power coupling efficiency measure fiber fact to power in the single-mode fiber, or 51% laser facet to power in the fiber, in good agreement with the predictions.

Tapered semiconductor optical amplifiers were reported1,2 recently with several watts of cw power near 980 nm in predominantly single-lobed and nearly diffraction-limited radiation patterns. The first demonstrations used Ti:sapphire master oscillators; subsequently, powers exceeding 1 W with good beam quality were demonstrated using all-semiconductor monolithic3 and hybrid4 master-oscillator/power-amplifier configurations. Similar tapered semiconductor devices can also be operated as lasers,5 offering greater simplicity of fabrication and use for some applications.

A two-stage erbium-doped fibre amplifier has been demonstrated with an output power of 700 mW at 1547 nm for 1 mW of input power. Tapered-gain-region semiconductor lasers were used as the pump source.<>

Introduction High power erbium-doped fiber amplifiers have many important applications. A key element for practical implementations is the availability of high power pump lasers efficiently coupled to single mode optical fiber. We have used fiber coupled tapered-gain-region semiconductor laser pumps at 975 nm to achieve 0.7 W of power at 1.5 μm using conventional erbium-doped fiber. This represents a significant advance over previous results because it avoids the use of Ti: Al2O3 lasers, which are not practical pump sources for many applications, and because direct pumping with conventional erbium fiber is more efficient than designs using co-doped fiber.

Semiconductor laser devices with tapered gain regions have recently generated much interest because they promise high output power with near-diffraction-limited spatial beam quality and good electrical to optical conversion efficiency. We report recent progress on two specific applications: a ring laser and a high- power erbium-doped fiber amplifier (EDFA). The ring laser operates unidirectionally in a single longitudinal mode with an output power of 170 mW and without a Faraday isolator. The high- power EDFA has an output power of 520 mW at 1.55 micrometers , the highest power reported to dates for an erbium-doped fiber amplifier using all semiconductor pump lasers. The common theme for both of these applications is the development of optical systems that produce high power in near-diffraction-limited collimated beams and efficient coupling into single mode optical fiber. We present an experimental procedure for quantitatively predicting the optical fiber power coupling efficiency. We have measured 64% power coupling efficiency measure fiber fact to power in the single-mode fiber, or 51% laser facet to power in the fiber, in good agreement with the predictions.