Fujikura Limited

Noboru Kawakami

Fumio Suzuki

Ryozo Yamauchi

Yoshio Kikuchi

Kuniharu Himeno

Osamu Fukuda

Tohru Arikawa

The optical fiber coupler of the present invention is characterized in that, for a defined section in which two or more component optical fibers are thermally fused and elongated thereby forming a fused-elongated region which constitutes the optical fiber coupler, that at least one of the component optical fibers is formed from a single mode optical fiber material employed within a parameter range in which the mode field diameter increases monotonically with decrease in the diameter of the optical fiber core. The optical fiber coupler is further characterized in that, when using optical fibers from which a portion of the coating material has been removed thereby exposing the cladding, and by aligning two or more of such component optical fibers side by side in a plane and mutually thermally fusing the exposed cladding of adjacent optical fibers, after which the fused region is drawn out, thereby forming a fused-elongated region which constitutes the optical fiber coupler, for such an optical fiber coupler, optical fiber material is used in which the softening temperature of the core is higher than that of the cladding, and further, for the drawing out of the mutually fused sections, the tension employed is such that by virtue of remaining stress, the refractive index of the core is reduced.

Optical fiber coupler

The present invention provides a wide wavelength range optical fiber coupler that to the greatest extent possible, allows optical coupling which is wavelength independent, and thus demonstrates a constant coupling ratio over a wide range of wavelengths. By causing various irregularities to be formed in the fused-elongated region of an optical fiber coupler, thereby leading to the generation of additional modes in addition to the fundamental modes, while at the same time causing multiple mode coupling in which the above mentioned additional modes participate in the coupling of the fundamental modes, it is possible to selectively control the coupling strength at determined wavelengths and thereby achieve optical coupling which is largely wavelength independent and thus demonstrates a relatively constant coupling ratio over a wide range of wavelengths. Furthermore, by causing the strength of coupling between the cores of each component optical fiber to vary along the length of the longitudinal axis of each component optical fiber, it is possible to decrease the degree of sinusoidal variation in the wavelength dependance characteristics of each component optical fiber, thereby making it possible to further achieve optical coupling which is wavelength independent and thus considerably constant over a wide range of wavelengths.

Optical fiber coupler and a fabrication method for the same

An optical fiber coupler is disclosed, which comprises two polished substrates each of which comprises a grooved substrate having a polished surface on the open side end thereof and adapted to hold therein an optical fiber and an optical fiber comprising a core, a cladding and two stress-applying parts arranged in the cladding so as to sandwich the core, a part of the optical fiber being polished off such that the polished surface of the fiber is close to the core so as to allow leakage of light power propagating in the core to the outside, the polished optical fiber being embedded in the grooved substrate and fixed thereto in such a manner that the polished surface of the grooved substrate is in flush with the polished surface of the polished optical fiber, with the two polished substrates being in close contact with each other at the polished surfaces thereof to allow coupling of light power, wherein said polished optical fiber is of a construction such that the polished surface thereof is perpendicular to the polarization principal axis X defined as the direction connecting the centers of said stress-applying parts. Also, a process for manufacturing the optical fiber coupler is disclosed.

Optical fiber coupler and process for manufacturing same

A optical fiber coupler manufacturing device is disclosed for the manufacture of fused-elongated type optical fiber couplers. The disclosed invention provides an optical fiber coupler manufacturing device having a chassis, a pair of movable stands provided within the chassis forming a space therebetween, optical fiber mounting units for mounting and fixing two or more component optical fibers on the above mentioned pair of movable stands, and a drive mechanism whereby the pair of movable stands can be driven back and forth in a direction parallel to the longitudinal axes of the component optical fibers. By virtue of the space formed between the two movable stands, a heat source can be applied to the aligned portions of the component optical fibers, thereby effecting thermal fusing of the aligned portions, after which drawing out of the thus fused section can be effected using the above mentioned drive mechanism for the movable stands, and additionally, a protective case for surrounding and reinforcing the manufactured optical fiber coupler can easily be applied without removing the optical fiber coupler from the apparatus through the above described space.

Growing community of inventors

Chiba, Japan

Noboru Kawakami