Apparatus for aligning optical source with optical fiber and optical source module having the same

Abstract: An apparatus is provided for aligning an optical source with an optical fiber to enable the optical fiber to receive a maximum of the light emitted from the optical source comprising: a substrate (100); said optical source (102) installed on the substrate; said optical fiber (106,306) aligned with the optical source for receiving light from the optical source; a holder (108,308) for holding the optical fiber; and a fixture (310) for fixing the holder, which includes a base (311) fixed on the substrate, a support (312) fixed on the base and having at least two portions spaced from each other by a distance enough to insert the holder in-between at least one protrusion (313) protruding from the support in a length direction of the optical fiber, and a connection portion (314,315) disposed at an end region of the protrusions, for connecting to the holder.

Description: The present invention relates generally to an apparatus for aligning an optical source with an optical fiber according to the generic clause of claim 1 and an optical source module having the same. Such an apparatus is already known from document EP-A-100 086, which discloses an apparatus for aligning an optical source with an optical fiber to enable the optical fiber to receive a maximum of the light emitted from the optical source, comprising: a substrate, said optical source installed on the substrate, said optical fiber aligned with the optical source for receiving light from the optical source, a holder for holding the optical fiber and a fixture for fixing the holder which includes a base fixed on the substrate, a support fixed on the base and having at least two portions spaced from each other by a distance enough to insert the holder in-between, and a connection portion for connecting to the holder. Generally, an optical source module having an optical source aligned with an optical fiber therein can be applied to any optical part which transmits/receives light, in particular, to a laser diode (LD) module, a semiconductor optical amplifier module, a 2.5-Gbit transmission/reception module, and a 155-Mbit transmission/reception module, which require high optical coupling efficiency. FIG. 1A is a schematic view of a conventional apparatus for aligning an optical source with an optical fiber. In FIG. 1A, the aligning apparatus includes an LD 102 installed on a substrate 100, a photo diode (PD) 104 aligned with the LD 102 on the substrate 100, an optical fiber 106 aligned with the LD 102, a ferrule 108 having the optical fiber 106 inserted thereinto, and a saddle 110 fixing the ferrule 110. Reference numeral 112 denotes soldering points. FIG. 1B is a sectional view of the conventional aligning apparatus shown in FIG. 1A, taken along line A-A'. The LD 102 is aligned with the optical fiber 106 in the following procedure. The LD 102 is first fixed on the substrate 100 and the ferrule 108 holding the optical fiber 106 is fixed to the saddle 110 by soldering. The saddle 110 is in turn fixed on the substrate 100. For alignment, an external driver (not shown) feeds current through the LD 102 and then light is emitted from the LD 102. The displacement of the ferrule 108 is regulated so that the optical fiber 106 can receive a maximum of the emitted light. At a maximum light receiving position, the saddle 110 is soldered to the ferrule 108. Here, soldering-caused deformation should be within an alignment error range. For application of the above mechanism to an optical fiber amplifier, the PD 104 is provided to measure the intensity of the light emitted from the LD 102 and feed back the measurement to the external driver, to thereby control the output of the LD 102. To allow the optical fiber 106 to obtain a high optical coupling efficiency from the LD 102, an end of the optical fiber 106 is formed into a lens of the same shape as the far field pattern of the LD 102 and aligned on multi-axes with the LD 102. In this case, the smallest alignment error range on an axis should be maintained at or below about 0.2µm. This conventional aligning apparatus, however, has the distinctive shortcoming of thermal expansion and contraction associated with soldering. More specifically, the portion at the center of the saddle 110 soldered with the ferrule 108 seriously incurs soldering deformation to the saddle 110 though soldering the bottom of the saddle 110 to the substrate 100 causes no deformation. FIG. 2A is a side view of an example of the ferrule and the saddle shown in FIG. 1A. As shown in FIG. 2A, an alignment error range along a vertical axis (y axis) is the smallest, about 0.2µm or below. Soldering a saddle 210 with a ferrule 208 at soldering points 212 after alignment of an optical source with an optical fiber 206 deforms the saddle 210 downward as indicated by reference numeral 220 due to soldering heat. That is, thermal deformation of about 10-20µm occurs along the y axis, deadly influencing optical coupling efficiency. A saddle 230 constituted as shown in FIG. 2B is also thermally deformed by about 5-10µm exceeding an alignment error range, along the y axis as indicated by reference numeral 231. It is, therefore, an object of the present invention to provide an apparatus for aligning an optical source with an optical fiber and an optical source module having the same, wherein a saddle has a protrusion in the length direction of the optical fiber to reduce thermal deformation of the saddle in the diameter direction of the optical fiber during soldering and the protrusion is soldered to a ferrule to prevent heat transfer in the diameter direction of the optical fiber. This object is solved by the apparatus of claim 1 and the module of claim 5. Preferred embodiments are disclosed in the dependent claims. In an aligning apparatus according to one aspect of the present invention, an optical source is installed on the substrate, an optical fiber is aligned with the optical source, for receiving light from the optical source, a holder holds the optical fiber to enable the optical fiber to receive a maximum of the light emitted from the optical source, and a fixture fixes the holder. The fixture includes a base fixed on the substrate and divided into two portions spaced from each other by a distance enough to insert the holder inbetween, a support having both ends integrally connected to the base, for supporting the holder inserted therein, a pair of protrusions extended from predetermined positions of both sides of the support along the length direction of the optical fiber, and a pair of connection portions disposed at both ends of each of the protrusions, for connecting to the holder. According to another aspect of the present invention, an apparatus for aligning an optical source with an optical fiber has a substrate, an optical source installed on the substrate, an optical fiber aligned with the optical source, for receiving light from the optical source, a holder for holding the optical fiber to enable the optical fiber to receive a maximum of the light emitted from the optical source, and a fixture for fixing the holder. In the fixture, a base is fixed on the substrate, a pair of supports are fixed on the base and spaced from each other by a distance enough to insert the holder inbetween, a protrusion extends from each support along the length direction of the optical fiber, and a pair of connection portions are disposed at both ends of the protrusion, for connecting to the holder. An embodiment of the optical source module has a box, a temperature sensor for sensing temperature inside the box, a temperature controller for controlling the temperature inside the box, and an apparatus for aligning an optical source with an optical fiber. In the aligning apparatus, an optical source is installed on the substrate, an optical fiber is aligned with the optical source, for receiving light from the optical source, a holder holds the optical fiber to enable the optical fiber to receive a maximum of the light emitted from the optical source, and a fixture fixes the holder. The fixture includes a base fixed on the substrate and divided into two portions spaced from each other by a distance enough to insert the holder inbetween, a support having both ends integrally connected to the base, for supporting the holder inserted therein, a pair of protrusions extended from predetermined positions of both sides of the support along the length direction of the optical fiber, and a pair of connection portions disposed at both ends of each of the protrusions, for connecting to the holder. Another embodiment of the optical source module includes a box, a temperature sensor for sensing temperature inside the box, a temperature controller for controlling the temperature inside the box, and an apparatus for aligning an optical source with an optical fiber. The aligning apparatus includes a substrate, an optical source installed on the substrate, an optical fiber aligned with the optical source, for receiving light from the optical source, a holder for holding the optical fiber to enable the optical fiber to receive a maximum of the light emitted from the optical source, and a fixture for fixing the holder. In the fixture, a base is fixed on the substrate, a pair of supports are fixed on the base and spaced from each other by a distance enough to insert the holder inbetween, a protrusion extends from each support along the length direction of the optical fiber, and a pair of connection portions are disposed at both ends of the protrusion, for connecting to the holder. The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which: FIG. 1A is a schematic view of a conventional apparatus for aligning an optical source with an optical fiber; FIG. 1B is a sectional view of the conventional aligning device of FIG. 1A, taken along line A-A'; FIG. 2A is a view illustrating an example of the ferrule and the saddle shown in FIG. 1A; FIG. 2B is a view illustrating another example of the ferrule and the saddle shown in FIG. 1A; FIG. 3A is a perspective view of an apparatus for aligning an optical source with an optical fiber according to a preferred embodiment of the present invention; FIG. 3B is a side view of the aligning apparatus shown in FIG. 3A; Fig. 3C is a front view of the aligning apparatus shown in Fig. 3A FIG. 4A is a perspective view of an apparatus for aligning an optical source with an optical fiber according to another preferred embodiment of the present invention; FIG. 4B is a side view of the aligning apparatus shown in FIG. 4A; FIG. 4C is a sectional view of the aligning apparatus shown in FIG. 4B, taken along line C-C'; FIG. 5A is a plan view of an optical module having an aligning apparatus according to the present invention; and FIG. 5B is a side view of the optical source module shown in FIG. 5A. Preferred embodiments of the present invention will be described hereinbelow with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. FIG. 3A is a side view of an apparatus for aligning an optical source with an optical fiber according to a preferred embodiment of the present invention. The aligning apparatus of FIG. 3A includes an optical source (not shown) fixed on a substrate (not shown), a holder 308 for holding an optical fiber 306, and a fixture 310 for fixing the holder 308. A ferrule is preferably used as the holder 308. The fixture 310 is comprised of a base 311 fixed on the substrate, a support 312 for supporting the holder 308, protrusions 313, and first and second connection portions 314 and 315 connected to the holder 308. The configurations and sizes of the components in the fixture 310 are determined by their thermal deformation, processing convenience, and mechanical strength. The base 311 is divided into two portions spaced from each other by a distance enough to insert the holder inbetween and both ends of the support 312 are integrally connected to the spaced portions of the base 311. FIG. 3B is a side view of the aligning apparatus shown in FIG. 3A and FIG. 3C is a sectional view of the aligning apparatus shown in FIG. 3B, taken along line B-B'. Alignment of an optical source with an optical fiber in the aligning apparatus will be described referring to FIGs. 3A, 3B, and 3C. Reference numeral 320 in FIG. 3B denotes a pair of pliers. An LD (not shown) as the optical source is fixed on the substrate by soldering. The holder 308 having the optical fiber 306 inserted therein is fixed to the fixture 310 by soldering. An end of the optical fiber 306 can be processed into a lens to increase an optical coupling efficiency. One end of the holder 308 is picked up and aligned by use of the pliers 320 so that the optical fiber 306 can receive the maximum of light emitted from the LD. Then, to compensate for vibrations generated in fixing the base 311, the holder 308 is positioned again using the pliers 320 and connected to the first connection portions 314 by laser soldering or brazing, preferably. When connecting the holder 308 to the first connection portions 314 by laser soldering, thermal deformation takes place along a z axis and thermal transfer along the y axis is prevented. Then, the holder 308 is subjected to fine adjustment with the pliers 320, for realignment and connected to the second connection portions 315. Let the distance between the first connection portions 314 and the input end of the optical fiber 306 be a and the distance between the first connection portions 314 and the second connection portions 315 be b . After the second connection portions 315 are soldered, the deformation of the optical fiber 306 can be reduced within an alignment error range according to an a to b ratio. FIG. 4A is a perspective view of an apparatus for aligning an optical source with an optical fiber according to another preferred embodiment of the present invention, FIG. 4B is a side view of the aligning apparatus shown in FIG. 4B, and FIG. 4C is a side view of the aligning apparatus shown in FIG. 4B, taken along line C-C'. The aligning apparatus of FIG. 4A includes an optical source (not shown) fixed on a substrate (not shown), a holder 408 for holding an optical fiber 406, and a fixture for fixing the holder 408. A ferrule is preferably used as the holder 408. The fixture is comprised of a base 411 fixed on the substrate, a support 412 for supporting the holder 408, a pair of supports 412, a pair of protrusions 413, and first and second connection portions 414 and 415 connected to the holder 408. The configurations and sizes of the components in the fixture are determined by their thermal deformation, processing convenience, and mechanical strength. The base 411 has an integrated structure. The supports 412 are integrally fixed on the base 411 and spaced from each other by a distance enough to insert the holder 408 inbetween. Alignment of the optical source with the optical fiber 406 in the second embodiment of the present invention is performed in the same manner as shown in FIGs. 3A, 3B, and 3C. FIG. 5A is a plan view of an optical source module having an aligning apparatus according to the present invention and FIG. 5B is a side view of the optical source module shown in FIG. 5A. Referring to FIGs. 5A and 5B, the optical source module includes an engine 500, an LD 502, a PD 504 for converting an optical signal to an electrical signal in order to measure the intensity of light emitted from the LD 502, an optical fiber 506 aligned with the LD 502, a holder 508 for fixedly holding the optical fiber 506, a fixture 510 for fixing the holder 508, a thermoelectric cooler 515 being a temperature controller and disposed under the engine 500, for maintaining temperature inside the optical source module to be constant, a thermister 520 being a temperature sensor, a box 524, a cover 526 covering the box 524, and a window ferrule 522 penetrating into the box 500, for protecting the optical fiber 506. Gases including nitrogen gas can be filled in the box 524. In the case of a 2.5-Gbit transmission/reception module or a 155-Mbit transmission/reception module, a ball lens can be further provided between the LD 502 and the optical fiber 506 in order to increase an alignment error range. In a semiconductor optical amplifier module, the PD 504 can be replaced with another optical fiber, for direct coupling. The LD 502 is aligned with the optical fiber 506 in the method shown in FIGs. 3A to 4C. The thermister 520 senses the temperature inside the optical source module to minimize deformation caused by temperature change during soldering components and maintain the performance of the LD 502 to be stable. The thermister 520 outputs a sensed temperature to the thermoelectric cooler 515 and the thermoelectric cooler 515 controls the temperature inside the module based on the sensed temperature. To reduce temperature-incurred deformation, it is preferable to form each component of a material having a low linear expansion coefficient. The substrate 500, the fixture 510, and the ferrule 508 are preferably of the same material since they are fixed by soldering. For example, the material can be nickel, a steel-nickel alloy, or SUS ("steel using stainless"). In the apparatus for aligning an optical source with an optical fiber and the optical source module having the aligning apparatus in accordance with the present invention, the fixture is modified in such a way to reduce thermal deformation of the fixture caused by soldering the holder to the fixture to fix the holder and thus the optical fiber can be aligned with the optical source within an allowable alignment error range. Therefore, the resulting increase of optical coupling efficiency enables fabrication of an optical source module with a higher output under the situation that an optical source with the same performance is used. Furthermore, the linear expansion of the fixture in the diameter direction of the holder is blocked, thereby increasing temperature reliability.

Claims: An apparatus for aligning an optical source with an optical fiber to enable the optical fiber to receive a maximum of the light emitted from the optical source, comprising: a substrate; said optical source (502) installed on the substrate; said optical fiber (306,406,506) aligned with the optical source for receiving light from the optical source; a holder (308,408,508) for holding the optical fiber; and a fixture (310,510) for fixing the holder, which includes a base (311,411) fixed on the substrate, a support (312,412) fixed on the base and having at least two portions spaced from each other by a distance enough to insert the holder in-between, and a connection portion (314,315,414,415) for connecting the holder, characterized in that the fixture (310,510) further comprises: at least one protrusion (313,413) protruding from the support in a length direction of the optical fiber, and in that the connection portion (314,315,414, 415) is disposed at an end region of the protrusion, for connecting to the holder. An apparatus for aligning an optical source with an optical fiber according to claim 1, wherein the base (311) is divided into two portions spaced from each other by a distance enough to insert the holder (308) in-between, said support (312) has both ends integrally connected to the base (311), for supporting the holder inserted therein, wherein a pair of said protrusions (313) extend from predetermined positions of both sides of the support (312) along the length direction of the optical fiber (306), and wherein a pair of said connection portions (314,315) is disposed at both ends of each of the protrusions (313), for connecting to the holder. An apparatus for aligning an optical source with an optical fiber according to claim 1, wherein said support comprises a pair of support parts (412) fixed on the base (411) and spaced from each other by a distance enough to insert the holder (408) in-between, wherein a protrusion (413) of said at least one protrusion extends from each support (412) along the length direction of the optical fiber (406), and a pair of said connection portions (414,415) is disposed at both ends of the protrusion (413), for connecting to the holder. The apparatus of claim 2 or 3, wherein the holder is connected to the connection portions by one of laser soldering and brazing. An optical source module comprising: a box (524); a temperature sensor (520) for sensing temperature inside the box (524); a temperature controller (515) for controlling the temperature inside the box (524); and an apparatus for aligning an optical source with an optical fiber according to any of the preceding claims.

Inventors: KWON OH-DAL, LIM SEONG-EUN, YUN TAE-WOO, KWON, OH-DAL, LIM, SEONG-EUN, YUN, TAE-WOO
Applicants: SAMSUNG ELECTRONICS CO LTD, SAMSUNG ELECTRONICS CO., LTD.
Application year: 2000
Main classification: G02B6
IPC codes: G02B6