Optimization of ASE source spectrum using FBG and VOA for enhanced spectral flatness and output power
OPTICS AND LASER TECHNOLOGY, cilt.204, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 204
- Basım Tarihi: 2026
- Doi Numarası: 10.1016/j.optlastec.2026.116352
- Dergi Adı: OPTICS AND LASER TECHNOLOGY
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Applied Science & Technology Source, Compendex, INSPEC, Academic Search Ultimate (EBSCO), Engineering Source (EBSCO)
- Gazi Üniversitesi Adresli: Evet
Özet
The Erbium-doped fiber (EDF) based Amplified Spontaneous Emission (ASE) light source provides excellent spectral properties in terms of its wide spectral coverage and long-term stability within the C + L band. However, as it is based on a strongly peaked emission profile around 1530 nm and 1592 nm, the ASE light source has a nonuniform spectral distribution. To improve spectral uniformity across the 1524-1604 nm window (80 nm), we tested two complementary approaches. First, we have used cascaded Fiber Bragg Gratings (FBGs) for selective back-reflection of wavelengths within the ASE spectrum. Second, we have employed a broadband variable optical attenuator (VOA) to provide wavelength-independent attenuation of the entire spectrum for global backreflection control. Both approaches were evaluated for their ability to minimize spectral ripple across this range. The experimental setup uses a double-pass bidirectional pumping configuration, with pump lasers at 974 nm and 1480 nm and 17 m of EDF. Our first measurements included only a broadband reflective mirror at the end of the double pass path. This resulted in a measured ripple of 7.13 dB. Next, we examined various single, dual and triple cascaded FBG structures. The triple cascaded FBG structure located at 1532 + 1544 + 1552 nm yielded a minimum ripple of 2.94 dB - a 59% reduction from the baseline. Ripple measurements of 1.07 dB over 28 nm and 1.17 dB over 36 nm were also reported in the sub-bands. Finally, for the VOA-based approach, we found that the optimal results were obtained at a level of 0.5 dB attenuation for achieving a ripple value of 3.08 dB. Furthermore, both methods maintained an approximately constant total output power of 13.9 dBm and demonstrated good spectral flattening without excessive loss of output power.