Monolithic wavelength-flattened 1 x 7 single-mode fused fiber couplers: theory, fabrication, and analysis.

The basic theory of monolithic 1 x 7 couplers is presented. The results of fabricating eighty-two devices are described, and the steady improvement in achieved device performance is shown leading to the fabrication of a controlled batch of eleven devices. These devices have excess losses of <0.1 dB together with good coupling uniformity to the seven output fibers. Maximum insertion losses are all around 10 dB or less, which is seen to compare favorably with devices obtained by concatenating 2 x 2 couplers. It is shown that to obtain an equal power split between the center and outer fibers it is necessary to control carefully the degree of fusion of the structure. An analysis of this coupling behavior is presented.

Polarization dependence of 4 x 4 optical fiber couplers.

The performance of monolithic 4 x 4 couplers is calculated as a function of arbitrary input polarization. By assuming polarization-independent diagonal coupling, an analytic result is obtained that is shown to agree with experiment. The effects of polarization-dependent diagonal coupling are calculated numerically. The measured polarization dependence of 4 x 4 fused fiber couplers is presented as a function of the degree of fusion of the fibers and is shown to be +/-0.5% for a medium fused device.

Theory and fabrication of 4 x 4 single-mode fused optical fiber couplers.

The theory, fabrication, and performance of monolithic 4 x 4 single-mode fused couplers is reported. The field coupling matrix is derived and used to show that a device having equal coupling between the four fibers may be obtained. The fabrication of such a device is described, and measurements show that the device exhibits excellent coupling uniformity and low excess loss. The wavelength response of a device designed for equal coupling at 1.53 microm is shown between 1.2 and 1.6 microm.

Theory and fabrication of wavelength flattened 1 x N single-mode couplers.

By using a theoretical model to describe coupling between an array of cores, it is shown that a range of monolithic wavelength flattened 1 x N couplers may be fabricated. Graphs of coupled power with coupling length are shown and the procedure for obtaining wavelength flattened devices is discussed for values of N ranging from 2 to 7. The fabrication and performance of a 1 x 7 coupler is described. The device has low excess loss (<0.3 dB) together with good coupling uniformity of <1% standard deviation at both 1.3 microm and 1.53 microm.

A Nd(3+)-doped cw fiber laser using all-fiber reflectors.

We demonstrate a novel all-fiber resonant optical cavity which uses two-fiber reflectors, each formed by a single loop of fiber between the output ports of a fiber directional coupler. The reflectivities of the fiber mirrors are each determined by the coupling ratio and the insertion loss of the fused couplers. When the cavity is formed in this way using a continuous length of Nd(3+)-doped fiber and pumped using a GaAs laser diode, lasing occurs at a wavelength of 1064 nm. Both theoretical and practical descriptions of the device are given.