Abstract: To obtain a narrow free-spectral range and controllable finesse,twin parallel channel waveguides are completely back coupled by a chirped Bragg grating,and cleaved facet mirrors are fabricated at the entrance of the coupling region.Thereby,the grating dispersion is introduced into the FabryPerot cavity,and the control of the cleaved facet mirrors on the finesse is maintained.The free-spectral range is determined not only by the cavity length,but also by the dispersion profile.A wide adjustment range of free-spectral range can be obtained by the adjustment of the grating profile.Numerical simulation and analyses show that the compression ratio of free-spectral range of the order of magnitude of 1000 can be obtained by this chirped Bragg grating F-P filter under the comparable device dimensions with conventional two-mirror F-P,and the free-spectral range will not be affected by the adjustment of finesse.