Optical fiber block

This invention provides an optical fiber block that includes an optical-fiber-alignment portion and a stress-reduction-depth portion. In the optical-fiber-alignment portion, a V groove array is arranged to accommodate the non-coated fiber portion of a ribbon fiber. The V groove array is formed by primary and secondary wet-etching processes on a silicon wafer, and further includes first V grooves at both sides and second V grooves different from the first V grooves disposed between the first V grooves. Meanwhile, the stress-reduction-depth portion is formed by another wet etching, extending to a predetermined depth from the optical-fiber-alignment portion, for reducing stress caused by a variation in the coating thickness of the optical fibers.

CLAIM OF PRIORITY

This application makes reference to and claims all benefits accruing under 35 U.S.C. Section 119 from an application entitled “Optical Fiber Block,” filed in the Korean Industrial Property Office on Jan. 4, 2002 and there duly assigned Serial No. 2002-415.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to an optical fiber block for connecting a Planar Lightwave Circuit (PLC) to an optical fiber and, in particular, to an optical fiber block for coupling a ribbon fiber.

2. Description of the Related Art

A PLC is an optical device in the form of a chip, which is widely used for division, modulation, switching, and multiplexing of optical signals. To connect a pLC to an optical fiber in alignment, an optical block is typically used. The optical fiber block is made of silicon materials and fabricated by wet-etching techniques.

FIG. 1illustrates a conventional PLC10used to connect the input of an optical block12and the output of optical fiber blocks14. As shown inFIG. 1, the optical fiber blocks12and14connect the PLC10to a single fiber F1and a ribbon fiber F2, respectively. A plurality of N wavelengths are inputted to the input port of the pLC10via the single fiber F1, then outputted to the ribbon fiber F2through the pLC10. The optical fiber blocks12and14are provided to fix the fibers F1and F2in alignment using an adhesive B, such as epoxy resin. Glass covers G1and G2are glued to the input and output sides of the PLC10, and glass covers G3and G4are glued to hold the optical fiber blocks12and14.

The alignment of the ribbon fiber F2using the optical fiber block14and the glass cover G4is further illustrated in FIG.2. After the optical fiber block14is combined with the glass cover G4, both are polished at a predetermined angle θ with respect to a vertical line L1. The resulting polished surface16acts to reduce optical loss.

FIG. 3illustrates the optical fiber block14in which a four-core ribbon fiber is to be placed. As shown inFIG. 3, the optical fiber block14is divided into an optical-fiber-alignment portion140in which a portion of the optical fibers with its coating removed are aligned thereon, and a stress-reduction-depth portion142to reduce the stress caused by the coating thickness of the ribbon fiber. A plurality of V grooves14ais arranged in the optical-fiber-alignment portion140. The stress-reduction-depth portion142is formed with high precision through the wet-etching techniques.

FIG. 4shows a perspective view of the optical fiber block14. As shown inFIG. 4, the optical fiber block14serves to fix the uncoated portion of the optical fibers BF that are aligned in the V grooves14awith equal pitches between them. Thus, it is essential to fabricate the V grooves14awith high precision, and the placement of the glass cover G4must be accurate. In addition, the alignment of the optical fibers BF must remain fixed using an adhesive B, such as epoxy resin.

However, the conventional optical fiber block generates the following problems in connecting a PLC to an optical fiber. A silicon wafer, from which the conventional optical fiber block is formed, exhibits specific etch characteristics according to the mask design due to its crystalline structure. This makes it impossible to form V-grooves with a 127-μm pitch. As a result, optical fibers may slip from the V grooves. In addition, as the optical fiber block is combined with a glass cover with a large space interposed between them, a large amount of epoxy is unnecessarily used. The extra epoxy may be contracted and expanded during the change in heat, thereby causing misalignment between an optical fiber array and the glass cover. Furthermore, the contraction and expansion of the epoxy is followed by its de-lamination, causing optical loss in the optical fiber component.

SUMMARY OF THE INVENTION

The present invention overcomes the above-described problems, and provides additional advantages by providing a highly reliable optical fiber block in which the influence of epoxy resin is minimized.

It is another aspect of the invention to provide an optical fiber block having V grooves in which bare optical fibers can be easily placed.

It is a further aspect of the present invention to provide an optical fiber block having a plurality of V grooves in which both ends of the V grooves are easily adapted to place the optical fibers therein.

The foregoing and other advantages of the present invention are achieved by providing an optical fiber block, which includes an optical-fiber-alignment portion and a stress-reduction-depth portion. In the optical-fiber-alignment portion, a V groove array is arranged to accommodate the bare optical fibers of a ribbon fiber. The V groove array is formed by primary and secondary wet etching on a silicon wafer, and contains first V grooves at both sides and second V grooves different from the first V grooves between the first V grooves. The stress-reduction-depth portion is formed by the primary wet etching extended to a predetermined depth from the optical-fiber-alignment portion, for reducing stress caused by a variation in the coating thickness.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following description, for purposes of explanation rather than limitation, specific details are set forth such as the particular architecture, interfaces, techniques, etc., in order to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced in other embodiments, which depart from these specific details. For purposes of simplicity and clarity, detailed descriptions of well-known devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.

To help understand the invention, an optical fiber block is an optical device that connects a PLC to an optical fiber in alignment. The optical fiber is placed in the optical fiber block, covered with a glass cover, and then fixed in alignment. The optical fiber block is aligned with a PLC and then fixed using an adhesive such as epoxy resin. This is a general way in which an optical fiber block is combined with a PLC. A Wavelength-Division Multiplexing (WDM) communication system uses a ribbon fiber as an output optical fiber for performing wavelength multiplexing. The output optical fiber may be a 4-core, 8-core, 16-core, or more than a 16-core fiber depending on the number of channels desired.

FIG. 5illustrates an optical fiber block20in which the optical fibers of a ribbon fiber are to be aligned according to a preferred embodiment of the present invention. As shown inFIG. 5, the optical fiber block20includes an optical-fiber-alignment portion210in which bare optical fibers of the ribbon fiber are aligned, and a stress-reduction-depth portion220that is etched to a predetermined depth. An array of V grooves212having first V grooves213and second V grooves214is formed along the optical-fiber-alignment portion210. The stress-reduction-depth portion220has a planar surface220aon which the portion of the bare optical fibers and the coated optical fibers are fixed. Here, the bare optical fibers represent optical fibers of the ribbon fiber from which the coatings are removed.

The optical-fiber-alignment portion210and the stress-reduction-depth portion220are formed on a silicon wafer by performing the wet-etching operation twice. The optical fiber block20shown inFIG. 5is designed for an 8-core optical fiber. For the V groove array212, both ends of the first V grooves213are formed larger than the second V grooves214disposed in the middle thereof.

FIGS. 6A and 6Billustrate the process of forming the V grooves on the optical fiber block20through a double wet-etching process in accordance with the techniques of the present invention. Referring to the drawings, a first etched portion E1and a second etched portion E2are formed on a silicon wafer S through the primary and secondary etch processes, respectively. In particular, the first and second etched portions E1and E2are defined by a photo-mask (not shown). The primary etching produces a planar first etched portion E1with a first predetermined depth on the silicon wafer S. The secondary etching produces a second etched portion E2containing the array of the V groves, with a second predetermined depth from the first etched portion E1. The second etched portion E2defines the stress-reduction-depth portion.

Referring back toFIG. 5, the first V grooves213and the second V grooves214are formed through the wet-etching process. The outer ends of the first V groves213are etched deeper than the second V grooves214. Therefore, when optical fibers are placed in the V grooves213and214, they are fully accommodated under the upper surface210aof the optical fiber block20.

Referring toFIGS. 7 and 8, the bare optical fibers aligned in the V grooves213and214are fixed using a glass cover and an epoxy resin. As the one end of the first V grooves213is larger than the second V grooves214, bare optical fibers are easily placed. In addition, since the bare optical fibers BF can be accommodated fully in the first and second V grooves213and214, a glass cover30is placed as close to the upper surface210aof the optical fiber block20as possible, thereby minimizing the influence of the epoxy B. The optical fiber block20and the glass cover30are polished along a polishing line L2inclined at a predetermined length θ.FIG. 8shows the optical fiber block20with the bare optical fibers after polishing.

In accordance with the present invention as described above, as the V grooves accommodate the bare optical fibers fully, the space between an optical fiber block and a glass cover is minimized when they are combined. This implies that a minimum amount of epoxy is used. Therefore, the influence of the epoxy is minimized, and the reliability of the device is improved. Furthermore, the ends of the outer V grooves are larger than the middle V grooves, thus facilitating alignment of the bare optical fibers in the optical fiber block.