Optical Filtering to Stabilize Fiber Amplifiers in the Presence of Stimulated Brillouin Scattering

Multistage fiber amplifiers play a crucial role in communications and data transport networks by enhancing signal power to maintain data integrity over long distances. There is an ongoing need for such amplifiers to handle ever-increasing data volumes and longer transmission distances, driven by the growth of internet usage, data centers, and communication networks. However, the amplification process comes with challenges. Nonlinear optical effects, most notably stimulated Brillouin scattering (SBS), can cause signal instabilities, limiting the power-handling capability of amplifiers. SBS causes a high-intensity pulse to propagate backward through the amplifier chain, potentially resulting in damage to upstream components and  thereby reducing the amplifier's efficiency and effectiveness. Current methods of handling intensity instabilities fall short, particularly when dealing with high power levels.

Technology Description

Multistage fiber amplifiers have the ability to amplify signal power from a range of a few Watts to several kilowatts. These devices, however, face limitations because of a sequence of nonlinear optical effects that causes intensity instabilities. Among these effects is stimulated Brillouin scattering (SBS), which generates a high-intensity pulse close to the signal wavelength, propagating backward and causing permanent damage to the components of the amplifier. One way to counter the effects of SBS is to install an optical isolator that blocks this backward-propagating light. However, with escalating power levels, the SBS pulse can produce light that propagates backward at wavelengths quite removed from the signal wavelength. For these situations, an effective solution is a filter with a broad reject band and a suppression ratio of or greater than 30 dB, which can stabilize amplifier stages and facilitate higher power operations.