Linewidth and alpha-factor of detuned-loaded DBR lasers

Linewidth of SG-DBR laser and its effect on DPSK transmission

“…By fitting the lineshape with Lorentzian, Gaussian and Voigt functions, we found that the lineshape of the SG-DBR laser is closer to the Voigt function. Similar results have also been found in other types of passive tuning laser diodes [13,17] which have been attributed to the 1/f carrier noise in the forward biased tuning region [18]. The selfheterodyne spectrum of the laser is the convolution of the Lorentzian spectrum associated with the white frequency noise and the approximately Gaussian spectrum arising from the 1/f noise [14].…”

“…The linewidth increases until the laser hops to the next mode while the SMSR is higher in the centre than the boundary of each mode. This behaviour has also been found in two-section DBR lasers and other similar devices [17]. In fact from Eqs.…”

“…This is caused by high threshold gain at the mode boundary, where the modes are not in the centre of the reflection peaks of the front and back gratings. This effect has also been found on other similar devices and been attributed to a detuned-loading effect [17].…”

“…It has been demonstrated that the laser linewidth is not correlated to the SMSR in [17] for two-section DBR lasers. It has also been shown in [23] that the linewidth of the channels of SG-DBR lasers can vary widely, even with similar SMSR and output power.…”

Characterization of a Low-phase-noise, High-power (370 mW), External-Cavity Semiconductor Laser

“…Reducing α should also reduce the 1/f noise, though this has not been proven explicitly. Reducing α has been shown to reduce the instantaneous linewidth by a factor of 7 [26]. Recent work [1] has also shown a factor of ten difference in the magnitude of the 1/f noise between ECSLs designed for digital applications as compared to analog applications, where linearity and chirp parameters have been optimized.…”