L-band amplifier uses backward ASE

March 1, 2002
Wavelength-division multiplexing systems that use the L-band (1570 to 1600 nm) typically pump this region the same way as the C-band is pumped, only with higher power to compensate for the lower gain. This results in noise from amplified spontaneous emission (ASE), which propagates both forward and backward. Mohd A. Mahdi at IOA Corp. (Sunnyvale, CA) and Harith Ahmad at the University of Malaya (Kuala Lumpur, Malaysia) developed a method to use the backward ASE to enhance L-band gain.1 Flat-gain values in excess of 24-dB and noise figures of 5 dB are obtained from the proposed amplifier.

They designed a two-stage amplifier, connected to the rest of the system with optical circulators (see figure). The first-stage amplifier provides low-noise characteristics and the second-stage amplifier, pumped by the backward ASE, produces high output powers.

The first-stage amplifier consists of a 980-nm laser diode that emits 120 mW of output power, and a 15-m-long erbium-doped fiber that has 240 ppm of erbium ion concentration. An isolator between the stages prevents lasing due to the ASE in a ring cavity.

The second-stage amplifier also contains a 980-nm laser-diode pump. Although the laser can supply 130 mW, the pump output power is varied with differing levels of ASE to result in a gain-flattened spectrum. In this case, the ASE acts as a pump source, raising the efficiency of the amplifier.

The active regions were pumped collinearly because that offers lower noise than counterpropagating pumping. They measured noise for the device as 5 dB. This device also allows more channels to be transmitted over the link than would be possible using a conventional amplifier.

For more information contact Mohd A. Mahdi at [email protected].

Yvonne Carts-Powell


  1. M. A. Mahdi and H. Ahmad, IEEE Photon. Tech. Lett 13(10), 1067 (October 2001).

Sponsored Recommendations

Scaling Moore’s Law and The Role of Integrated Photonics

April 8, 2024
Intel presents its perspective on how photonic integration can enable similar performance scaling as Moore’s Law for package I/O with higher data throughput and lower energy consumption...

Coherent Routing and Optical Transport – Getting Under the Covers

April 11, 2024
Join us as we delve into the symbiotic relationship between IPoDWDM and cutting-edge optical transport innovations, revolutionizing the landscape of data transmission.

Moving to 800G & Beyond

Jan. 27, 2023
Service provider and hyperscale data center network operators are beginning to deploy 800G transmission capabilities – but are using different technologies to do so. The higher...

Constructing Fiber Networks: The Value of Solutions

March 20, 2024
In designing and provisioning a fiber network, it’s important to think of it as more than a collection of parts. In this webinar, AFL’s Josh Simer will show how a solution mindset...