Product Spotlight: Optical Pumping Yields High-Power Pump Laser for EDFAs

Editor's Report
By pumping a vertical cavity surface-emitting laser with an edge-emitting laser, engineers at Coherent, Inc. (Santa Clara, CA) have generated a minimum of 500 mW of fiber-coupled power at 980 nm, making the devices attractive for use with erbium-doped fiber amplifiers.

EDFAs are the workhorses of optical networks, beefing up the optical signal between fiber spans to enhance transmission. Device gain depends on pump power, generating keen interest in high power pump sources. Typically, those sources are diode lasers operating at 980 nm or 1480 nm. To provide necessary pump power, several lasers are often coupled into a single EDFA, increasing cost and complexity of the amplifiers.

At the Optical Fiber Communication (OFC) Conference (March 5-10; Baltimore, MD), pump laser specialists like SDL Inc. (San Jose, CA) were touting 980 nm emitters with output specifications of 300 mW.

Device design
The OPSL-980 device consists of an aluminium semiconductor material VCSEL pumped with a 2 W aluminium-free broad area diode operating at around 800 nm Prototype devices have generated a minimum of 500 mW of output power, with approximately 85 to 90% coupling into an output fiber. The design is power scalable, according to vice president of telecom Jean-Michel Pelaprat, and output could reach as high as 1 W.

The device operates in single transverse mode (TEM₀₀), generating stable single-frequency output. Power density on the semiconductor "endfaces" is reduced by a factor of up to 100 below that of edge-emitting devices, which bodes well for device lifetime and power scalability.

The development program has completed phase I, which included field trials with deployed EDFAs. The prototype OPSL-980's shipped to date are not packaged for telecom field deployment. Phase II will focus on package modification to meet Bellcore standards.