Amplified Transmission Beyond C- and L- Bands: Bismuth Doped Fiber Amplifier for O-Band Transmission

Optical amplification beyond C- and L-bands may be a promising solution to increase the capacity of transmission systems. In this paper we reviewed different amplification technologies, including semiconductor optical amplifiers (SOA), Raman amplifiers and doped fiber amplifiers briefly discussing their advantages and disadvantages. We found that while a variety of amplification solutions are available, they have not been implemented in practical systems because, until recently, C- and L- bands EDFA amplified systems provided sufficient capacity, and the lack of a complete optical components ecosystem. The O-band (1260–1360 nm) may be a notable exception since it has been used for decades for unamplified point-to-point transmission near fiber zero dispersion wavelength. Overall capacity demand and power budget reduction caused by the bit rate increase of pluggable modules promises to make O-band amplification an attractive solution. We present simple broadband O-band bismuth doped fiber amplifier (BDFA) with characteristics similar to, or above commercially available EDFAs. We demonstrated that BDFAs can amplify the entire O-band and a single stage amplifier can deliver 20 dB gain, 18 dBm output power and 5.5 dB noise figure over the 3-dB bandwidth greater than 60 nm. We illustrated the application of BDFAs by transmitting signals from a commercial 400 Gb/s 8-channel LAN-WDM transponder, operating within the IEEE standardized band, over 50 km of legacy G.652 fiber. We also demonstrated high power BDFA capable of delivering more than 700 mW of optical power without inducing measurable nonlinear distortion to intensity modulated signal propagating over a dispersive fiber waveguide.