The explosive growth of Internet traffic leads to increasing demands for communication bandwidth. Meanwhile, the size, power and cost requirements of the optical links are also imposed. It has been recognized that the spectral width and the mode partition noise (MPN) of the multi-mode lasing source are major limiting factors in high-speed, yet cost-sensitive fiber-optic communication systems, such as Gigabit-capable passive optical networks and fiber channel for optical interconnections. Aiming at pushing the performance limit of conventional Fabry-Perot (FP) lasers for higher bit-rates in a cost-effective fashion, this paper proposed a compact structure based on the FP cavity incorporating a built-in wavelength detuned band-pass filter (BPF) near one end of the cavity as shown in Fig. 1. The effective index of the widened ridge will be higher than that of the non-widened one, and the interface at which the ridge width changes and its nearest cavity facet form a FP etalon. A short tapering region is introduced before the wide ridge section to further increase the refractive index difference at interface 2. The designed structure is simulated by the broadband optical traveling wave model. Simulation results shown in Fig. 2 show that this design is able to narrow the optical spectrum significantly from 16nm to around 8nm and the −20 dB bandwidth is decreasing slightly with the increase of the detuning until around 3.2nm and the adjacent pass-band starts to acquire sufficient gain within the gain bandwidth and take effect on broadening the bandwidth with further increase of the detuning. We have fabricated the 1310nm strained layer multiple quantum well laser with presented design of the ridge. The typical measured optical spectra for the proposed structure and a reference FP laser that was fabricated on the same wafer are shown in Fig. 3. It is observed that the measured RMS width is almost narrowed by half as expected. We have also simulated the devices' performance in transmission at 2.5 Gbit/s and 10 Gbit/s over the standard single-mode fiber in the GPON infrastructure. The typical upstream wavelength is 1310 nm, which however will shift with the temperature at a typical changing rate of 0.55 nm/°C for InAlGaAs active region. We therefore investigate the dependence of BER on the received power when the lasing wavelength shifts to 1343nm at an elevated temperature of 85 and show the results in Fig. 4. A power penalty of only 1 dB for an error rate of 10−12 applies to transmission over 21km and 6.1km under the modulation speed of 2.5 Gbit/s and 10 Gbit/s, respectively, for the proposed one. On the contrary, the large error floor shown in the FP case indicates a severe MPN effect, causing the power penalty greatly exceeding the allowed value. The experiment for system transmissions is ongoing. In conclusion, with compact structure and easy fabrication, the proposed laser exhibits a much narrower spectral width and the noticeable better simulated transmission performances over the conventional FP lasers, and is expected to find its potential applications in cost-sensitive short-reach fiber transmission system.