The present invention provides environmentally stable interferometric and lattice devices that exhibit low excess loss and polarization dependent loss. The modal noise at the splices between the device pigtails and the system fiber is minimized or eliminated. The present invention is an optical device (10) for filtering a light signal. The optical device (10) has a tunable spectral response. The optical device includes a first optical fiber (25) having a first core region (30) and a cladding (34) with refractive index n2. The first core region (30) includes a core (32) having refractive index n1 and a first fiber coupling regulator (300) integral with the first optical fiber (25). The first fiber coupling regulator (300) couples the light signal between a first optical path and second optical path and substantially prevents the light signals from coupling into a third optical path.