摘要
通过增加光纤放大器的增益带宽,可以有效提升光纤通信系统的传输容量。目前,C+L波段掺铒光纤放大器(EDFA)通常采用C波段和L波段EDFA并联的方式,但这种方法会在两个增益波段之间产生带宽“死区”。为了解决这一问题,以Bi/Er共掺石英光纤作为主要增益介质,在二级双程放大结构的基础上,通过插入波长匹配的长周期光纤光栅进行“削峰补谷”操作,成功拓展了增益带宽。这种新型的C+L波段全覆盖高增益掺铒光纤放大器,其25 dB增益带宽和20 dB增益带宽分别达到了78 nm(1529~1607 nm)和85 nm(1527~1612 nm),最高增益可达51.2 dB,同时噪声系数降至3.9 dB。该研究不仅消除了C+L波段EDFA的带宽“死区”问题,而且通过结合长周期光纤光栅,实现了单个EDFA对C+L波段的高增益全覆盖。该EDFA有望在未来高容量长距离光纤传输系统中获得重要应用。
Objective Increasing the gain bandwidth of optical fiber amplifiers is the simplest and most effective method for improving the transmission capacity of optical fiber communication systems.Currently,C+L-band erbium-doped fiber amplifiers(EDFAs)are typically formed by parallel C-and L-band EDFAs,without any gaps between the two bands.Therefore,the research and development for an EDFA with a high gain bandwidth that fully covers the C+L band,have always garnered attention.However,the initially designed C+L band EDFA either fails to cover the gain bandwidth within entire C+L band or suffers from low gain levels and high noise,unable to fully meet the requirements of long-distance transmission systems.In this study,a C+L-band full-coverage high-gain EDFA is realized using a Bi/Er co-doped fiber as the main gain medium in a two-stage double-pass amplification structure with a long-period fiber grating inserted to shave the gain peak and fill the valley with 25 dB and 20 dB gain bandwidths corresponding to 78 nm(1529‒1607 nm)and 85 nm(1527‒1612 nm),respectively.The maximum gain reaches 51.2 dB,and the minimum noise is 3.9 dB,achieving a sufficiently high gain in a broad gain bandwidth covering the entire C+L-band,indicating a high potential for widespread use in future high-capacity long-haul optical fiber transmission systems.Methods To increase the gain level and control noise,the amplifier uses a two-stage double-pass amplification structure.The main amplifier has an 8 m long bismuth/erbium co-doped silica fiber(BEDF)as the gain medium,which is bidirectionally pumped by a pair of 1480 nm laser diodes.The BEDF is fabricated using the atomic layer deposition(ALD)method in conjunction with modified chemical vapor deposition(MCVD).In addition to the co-doped elements of Bi(mole fraction of 0.004%)and Er(mole fraction of 0.109%),Al,P,and Ge are also included.This fiber exhibits a background loss of 0.02 dB/m at 1200 nm and an absorption coefficient of 22 dB/m at 1531 nm.For the pre-amplifier,a 2 m high-concentration EDF is used as the gain medium,which is forward pumped by a 980 nm laser diode(LD)with a pump power of 100 mW.A fiber ring mirror consisting of an optical circulator(circulator 2)is connected at the end of the main amplifier,which is used to route the amplified input signals and the forward-amplified spontaneous emission(ASE)back into the amplifier system to achieve double-pass amplification.The gain bandwidth is expanded by inserting a wavelength-matched long-period fiber grating between the main amplifier and fiber ring mirror.To investigate the role of LPG in a high-gain EDFA with full coverage in the C+L band,the gain and noise are tested in two separate scenarios,with and without an LPG inserted between ports 1 and 3 of circulator 2.These two structures are referred to as“comparison structure 1”and“comparison structure 2,”respectively.The amplifier structure(shown in Fig.1)is designated as the“reported structure.”Results and Discussions The experimental results on measurement gain and noise of the three EDFA structures under the same experimental conditions are displayed in Fig.4.Clearly,the gain spectra of all three amplifier structures cover the C+L band region,extend to 1620 nm on the long-wavelength side,and provide a broader wavelength range than conventional EDFAs.Additionally,the gain level in the L-band,which is closely related to the broad-spectrum gain characteristics of the Bi/Er co-doped fibers,is enhanced.Among the three structures,the reported structure for the amplifier exhibits a significantly broader gain bandwidth than those of structures 1 and 2.Specifically,the 25 dB and 20 dB gain bandwidths reach 78 nm(1529‒1607 nm)and 85 nm(1527‒1612 nm),respectively,fully covering the entire C+L band.In terms of noise performance comparison,all three structures maintain a relatively low noise of below 6 dB within the wavelength range of 1545‒1608 nm.This is primarily attributed to the incorporation of a preamplifier because the noise of the two-stage amplifier architecture is predominantly determined by the noise of the first-stage amplifier.Compared with the main performance parameters of C+L-band EDFAs reported in recent years(Table 1),the C+L-band EDFA demonstrated in this study exhibits the best comprehensive performance:a high gain level,low noise,and a 25 dB gain bandwidth that completely covers the C+L-band.Conclusions Using Bi/Er co-doped silica fiber as the primary gain medium and a two-stage double-pass amplification structure,this study employs long-period fiber gratings to expand the gain bandwidth.Consequently,a high-gain erbium-doped fiber amplifier with full coverage of the C+L band is achieved.The 25 dB and 20 dB gain bandwidths reach 78 nm(1529‒1607 nm)and 85 nm(1527‒1612 nm),respectively,with a maximum gain of 51.2 dB and minimum low noise of 3.9 dB.Compared with the Bi/Er co-doped fiber C+L band EDFA reported in recent years,this amplifier not only exhibits high gain and low noise but also achieves full coverage of the C+L band with 25 dB gain bandwidth.Its superior overall performance is expected to lead to important applications in future high-capacity long-haul optical fiber transmission systems.
作者
邹泳芳
董新永
巫智凯
文建湘
王廷云
汪松
王云才
秦玉文
Zou Yongfang;Dong Xinyong;Wu Zhikai;Wen Jianxiang;Wang Tingyun;Wang Song;Wang Yuncai;Qin Yuwen(Institute of Advanced Photonics Technology,School of Information Engineering,Guangdong University of Technology,Guangzhou 510006,Guangdong,China;Key Laboratory of Photonic Technology for Integrated Sensing and Communication,Ministry of Education,Guangdong University of Technology,Guangzhou 510006,Guangdong,China;Guangdong Provincial Key Laboratory of Information Photonics Technology,Guangdong University of Technology,Guangzhou 510006,Guangdong,China;Key Laboratory of Specialty Fiber Optics and Optical Access Networks,Shanghai University,Shanghai 200444,China;State Key Laboratory of Optical Fiber and Cable Manufacture Technology,Yangtze Optical Fiber and Cable Joint Stock Limited Company(YOFC),Wuhan 430073,Hubei,China)
出处
《中国激光》
EI
CAS
CSCD
北大核心
2024年第18期201-206,共6页
Chinese Journal of Lasers
基金
国家重点研发计划(2020YFB1805804)
国家自然科学基金国际(地区)合作与交流项目(62361136584)
广东省“珠江人才计划”引进创新创业团队项目(2019ZT08X340)。
