BIDIRECTIONAL OPTICAL MODULE

A bidirectional optical module for communicating optical signals bidirectionally via a single optical fiber is provided. The bidirectional optical module includes an optical fiber, a stem having a cavity formed at one side thereof and first alignment marks formed near an entrance of the cavity, a light emitting device mounted on the cavity, a light receiving device mounted on the cavity and spaced apart from the light emitting device, a filter block part fixed near the entrance of the cavity and configured to deliver light output from the light emitting device to the optical fiber and deliver light input through the optical fiber to the light receiving device, and a cap configured to accommodate the light emitting device, light receiving device, and a filter block part between the cap and the stem.

DETAILED DESCRIPTION

Hereinafter, preferred embodiments of the present invention will be described below in more detail with reference to the accompanying drawings.

FIG. 1is a side sectional view of a bidirectional optical module according to an embodiment of the present invention.FIG. 2is an exploded perspective view ofFIG. 1.FIG. 3is a perspective view of first and second support blocks as shown inFIG. 2.

Referring toFIGS. 1 to 3, the bidirectional optical module100includes an optical fiber110, a cap120, a stem130, a light emitting device140, a light receiving device150, and a filter block part160.

The optical fiber110receives input light2dfrom the outside and then transmits input light λ1to the light receiving device150, and receives output light λ2from the light emitting device140and then transmits output light λ2to the outside. The optical fiber110may be supported in a holder111. The holder111may be inserted into and combined with a hole that is formed in the cap120.

In the holder111, a focusing lens112may be supported. The focusing lens112is positioned between the optical fiber110and the filter block part160. The focusing lens112may focus light that is output from the light emitting device140and transmitted through the filter block part160to deliver the focused light to the optical fiber110. The focusing lens112may be formed of a ball lens, etc.

The cap120has an inner space. The cap120may have a hole at its upper portion, where the holder111may be combined, and an opening structure at its lower portion. The opening structure at the lower portion of the cap120may be fixed along the top edge of the stem130, thereby sealing the inner space of the cap120. The sealed space of the cap120may accommodate and protect the light emitting device140, the light receiving device150, and the filter block part160.

The stem130has a cavity131formed thereon. The light emitting device140and the light receiving device150are mounted on the cavity131. As shown inFIG. 2, the cavity131may be formed to have a concave shape recessed at a certain depth from the top of the stem130. Moreover, the top edge of the stem130may be recessed to the depth of the cavity131. The opening at the lower portion of the cap120may be fixed at the recessed top edge of the stem130.

The cavity131may have a partition wall132formed to separate the light emitting device140and the light receiving device150. The partition wall132may be formed to have a height corresponding to the depth of the cavity131. The partition wall132can minimize interference between light λ2emitted from the light emitting device140and light λ1incident on the light receiving device150. First alignment marks133are formed near the entrance of the cavity131. The stem130may be a transistor outline stem (TO stem).

The light emitting device140is mounted on the cavity131. The light emitting device140may be formed of a laser diode, etc. The light receiving device150is also mounted on the cavity131separately from the light emitting device140. The light receiving device150may be formed of a photo diode, etc. A trans-impedance amplifier151is an amplifier that converts a current signal, which is output from the light receiving device150, to a voltage signal, and may be mounted at one side of the light receiving device150.

The light emitting device140and the light receiving device150may be mounted on the cavity131and die-bonded or wire-bonded on the stem130. At this point, the light emitting device140and the light receiving device150may be mounted using an alignment mark (not shown), thereby minimizing an alignment error.

The filter block part160is fixed near the entrance of the cavity131. The filter block part160delivers output light λ2output from the light emitting device140to the optical fiber110and delivers input light λ1input through the optical fiber110to the light receiving device150. That is, the filter block part160optically couples the light emitting device140and the optical fiber110, and also optically couples the optical fiber110and light receiving device150.

For example, the optical fiber110and the light emitting device140may be disposed to corresponding to each other. The filter block part160may allow output light λ2from the light emitting device140to pass therethrough to the optical fiber110and reflect input light λ1input through the optical fiber110to deliver the reflected light to the light receiving device150.

To this end, the filter block part160may include a first support block161, a second support block162, a first optical filter163, and a second optical filter164. The first support block161and the second support block162may each have a right triangular prism shape with a 45 degree inclined plane.

The first optical filter163is provided on the 45 degree inclined plane of the first support block161. The first optical filter163passes only light λ2in a wavelength band that is output from the light emitting device140therethrough and reflects light in other wavelength bands. The second optical filter164is provided on the 45 degree inclined plane of the second support block162. The second optical filter164reflects light λ1in other wavelength bands that is input through the optical fiber110. The first and second optical filters163and164may each be formed of a wavelength-division multiplexing (WDM) thin film filter. Alternatively, the second optical filter163may be formed of a reflection mirror. The first and second optical filters163and164may be fixed to the first and second support blocks161and162using ultraviolet epoxy.

The first and second support blocks161and162may be fixed near the entrance of the cavity131in such a manner that the first optical filter163passes output light λ2output from the light emitting device140therethrough to deliver the output light λ2to the optical fiber110and the first optical filter163and then the second optical filter164sequentially reflect input light λ1input through the optical fiber110to deliver the input light λ1to the light receiving device150.

That is, while the first support block161is disposed on the top of the light emitting device140, the second support block162is disposed on the top of the light receiving device150. In this case, the first optical filter163is disposed to reflect input light λ1input from the optical fiber110at 45 degrees to deliver the reflected light to the second optical filter164. Also, the second optical filter164is disposed to reflect input light λ1, which is reflected by the first optical filter163, at 90 degrees to deliver the reflected light to the light receiving device150.

The first support block163has a first through hole161aformed on an area through which output light λ2output from the light emitting device140passes. The first through hole161ahas a path corresponding to a path of output light λ2being output from the light emitting device140and then straightly delivered to the optical fiber110.

The second support block162has a second through hole162aformed on an area through which input light λ1input through the optical fiber110passes after passing through the first optical filter163and then the second optical filter164. The second through hole162ahas a path corresponding to a path of input light λ1being reflected by the first optical filter163at 45 degrees, delivered to the second optical filter164, reflected by the second optical filter164at 90 degrees, and then input to the light receiving device150. The first and second support blocks161and162may each be formed of a plastic injection molding product that is injected into a mold. Accordingly, the first and second support blocks161and162can be manufactured on a large scale at a low cost.

The first support block161may have an entrance of the first through hole161athat is positioned on a bottom surface of the first support block161and provided with a first lens171at the entrance of the first through hole161a.The first lens171is intended to reduce a radiation angle of output light λ2output from the light emitting device140. The first lens171is formed of a hemispherical lens, a convex part of which may be disposed toward the light emitting device140.

The second support block162may have an exit of the second through hole162athat is positioned on a bottom surface of the second support block162and provided with a second lens172at the entrance of the second through hole162a.The second lens172is intended to focus input light λ1reflected by the second optical filter164. The second lens172is formed of a hemispherical lens, a convex part of which may be disposed toward the light receiving device150. A first wavelength blocking filter173may be inserted between the entrance of the first through hole161aand the first lens171. A second wavelength blocking filter174may be inserted between the exit of the second through hole162aand the second lens172. The first and second wavelength blocking filters173and174each block a specific wavelength band, thereby reducing optical crosstalk. The first and second wavelength blocking filters173and174may be fixed in the first and second support blocks161and162using ultraviolet epoxy. Furthermore, the first and second lenses171and172may be fixed in the first and second wavelength blocking filters173and174using ultraviolet epoxy.

The invention should not be construed as being limited to the examples illustrated herein. The optical fiber110and the light receiving device150may be disposed to correspond to each other, and the filter block part160may allow light λ1input through the optical fiber110to pass therethrough to the light receiving device150and reflect light λ2output from the light emitting device140to deliver the reflected light to the optical fiber110.

The filter block part160has second alignment marks165. When the filter block part160includes the first and second support blocks161and162, the first and second support blocks161and162each have the second alignment marks165. The second alignment marks165correspond to the first alignment marks133such that the first and second support blocks161and163may be aligned near the entrance of the cavity131.

Accordingly, as shown inFIG. 4, the second alignment marks165correspond to the first alignment marks133such that the first and second support blocks161and162may be passively aligned near the entrance of the cavity131. In this case, an alignment jig may be used to align the first and second support blocks161and162near the entrance of the cavity131. After the first and second support blocks161and162are aligned near the entrance of the cavity131, the first and second support blocks161and162may be fixed near the entrance of the cavity131using ultraviolet epoxy. In this way, the first and second support blocks161and162may be passively aligned with the stem130, thereby enhancing the productivity of the bidirectional optical module100.

The stem130may have third alignment marks134formed on the top edge of the stem130. The cap120may have fourth alignment marks121corresponding to the third alignment marks134, thereby being aligned with the stem130. Accordingly, as shown inFIG. 5, as the fourth alignment marks121are aligned with the third alignment marks134, the cap120may be passively aligned with the stem130. Before the cap120is aligned with the stem130, a sealing process for sealing with the cap120may be performed on the stem130Furthermore, after the cap120is aligned with the stem130using the third alignment marks134and the fourth alignment marks121, the cap120may be fixed by laser welding. As another example, the cap120and the stem130can be actively aligned using a method of measuring an output of light output from the optical fiber110.

According to the present invention, the filter block part can be passively aligned with the stem having the light emitting device and the light receiving device mounted side by side, thereby enhancing the productivity of the bidirectional optical module.

According to the present invention, the filter block part has a structure in which the first and second support blocks formed of an injection molding product of a right triangular prism shape are each provided with a thin film filter. Thus, the filter block part can be manufactured on a large scale at a low cost.

Accordingly, the present invention can be effectively and easily applied to the manufacturing of a low-price bidirectional optical module, using a large diameter optical fiber such as a multi-mode fiber and a plastic optical fiber (POF).