Investigation of Chirp–Fiber Dispersion Interaction of 850 nm and 880 nm Self-Injection-Locked VCSELs and Extended Reach Data Transmission over Standard Single-Mode Fiber

Self-injection-locked (SIL) VCSELs enable optically coupled apertures to operate as a coherent supermode, combining the high power of multi-aperture devices with quasi-single-mode emission, narrowing far-field beam divergence, and simplified coupling into single-mode fiber. In this work, SIL VCSELs operating near 850 and 880 nm were characterized to examine whether their chirp properties remain favorable for extended-reach short-wavelength transmission. More than 29% coupling efficiency into a single-mode fiber (Hi780) was achieved for both devices using a two-lens coupling arrangement. Link transfer functions were measured over a long single-mode fiber, Hi780, and via a standard single-mode fiber, with fundamental-mode launch via a spliced section of Hi780. The dominant transient chirp behavior is preserved for SIL VCSEL similar to the case of single-mode (SM) VCSEL and multi-aperture (MA) SM VCSELs. A unified full-spectrum fitting method was introduced to extract physically consistent chirp and chromatic-dispersion parameters from shallow transfer-function dips, with the chirp parameter determined to be approximately −2.6. Using the 850 nm SIL VCSEL, 32G NRZ transmission over 1 km of a standard single-mode fiber with fundamental mode launch was demonstrated. Compared with the back-to-back configuration, the 1 km link produced a more open eye and improved 7-tap FFE equalized Gaussian BER from 7.56 × 10−13 to 1.53 × 10−14, confirming chirp–dispersion-induced bandwidth enhancement.