Shanghai Institute of Optics and Mechanics proposes a new scheme of Er doped silicate fiber as an extended L-band broadband amplifier

Recently, Hu Lili, a research group of the Advanced Laser and Optoelectronic Functional Materials Department of the Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, proposed a new scheme based on field strength optimization of Er doped silicate fiber as an extended L-band broadband amplifier. Relevant research achievements were published in Optics Letters under the title of "Er doped silicate fiber amplifiers in the L-band with flat gain".

The rapid development of big data and artificial intelligence has put forward higher requirements for the capacity of dense wave division multiplexers (DWDMs) in the new generation of optical communication systems. Compared to the mature C-band (1530-1565nm) erbium-doped fiber amplifier (EDFA), the L-band (1565-1625nm) EDFA has become a new generation of scalable optical communication products. However, the development of L-band EDFA faces difficulties and challenges: the gain of Er-doped fibers is limited by low longwave emission cross-sections and severe excited state absorption, resulting in very small gains for wavelengths greater than 1600nm. Therefore, how to improve the long wave gain of Er doped fiber materials is a key scientific problem that urgently needs to be solved in L-band broadband amplifiers.

The research team proposes a new scheme of micro ion field emphasis control to enhance the gain and spectral shaping of Er ions in a silicate fiber matrix. The feasibility of using silicate optical fibers as long wave gain enhancing substrates for Er ions has been confirmed both theoretically and experimentally. This scheme has achieved significant improvement in L-band gain and optimization of gain flatness in Er doped silicate optical fibers. At the same time, by adopting an all fiber scheme with heterogeneous fiber fusion, only a 1.5m long silicate fiber is used. At the longest wavelength of 1625nm in the L-band, the gain coefficient is 4.7dB/m, which is better than the 0.3dB/m of quartz fiber. In addition, the gain flatness of the fiber in the L-band is 0.8dB, which is better than the 5dB of quartz fiber. Compared to quartz fiber, this fiber has a higher doping concentration, shorter usage length, and larger gain coefficient, providing key material support for the new generation of L-band EDFA.

This work has received support from the National Natural Science Foundation of China and national key projects.

Figure 1: L-band gain of Er doped silicate optical fiber

Source: Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences