Patent Publication Number: US-2018039033-A1

Title: Multi-channel optical module and manufacturing method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a divisional application of U.S. patent application Ser. No. 14/841,158, filed on Aug. 31, 2015. Further, this application claims priority to and the benefit of Korean Patent Application No. 10-2014-0115621, filed on Sep. 1, 2014, in the Korean Intellectual Property Office. The entire contents of these prior U.S and Korean applications are hereby incorporated by reference. 
    
    
     BACKGROUND 
     Field of Invention 
     Various embodiments of the present disclosure relate to a multi-channel optical module and a manufacturing method thereof, and more particularly to a multi-channel optical module configured to transmit and/or receive an optical signal for optical communication of multiple channels (hereinafter referred to as an optical signal), and a manufacturing method thereof. 
     Description of Related Art 
     As various kinds of multimedia services are emerging these days, the need to exchange massive amounts of information has increased, which has caused an increase of amount of data being transmitted through a network. In response to such increased amount of data, an optical communication system of wavelength division multiplexing (hereinafter referred to as WDM) is being widely used. The WDM method is a method of transceiving data of numerous wavelength bands through one optical fiber after multiplexing or de-multiplexing. 
     In such a WDM-based optical communication system, a multi-channel optical module such as a transmitter optical sub assembly (TOSA), receiver optical sub assembly (ROSA), or optical sub assembly (OSA) is necessary in order to multiplex a data channel. Especially, since a metro network system that transmits massive data needs to have a long data transmission distance and fast data transmission speed, it is necessary to provide a high capacity high performance multi-channel optical module. 
     The multi-channel optical module may be a data receiving device that converts optical signals being received in parallel through an optical fiber or de-multiplexer into electric signals or a data transmitting device that converts electric signals into optical signals and transmits the converted optical signals through an optical fiber or multiplexer. Such a multi-channel optical module performs alignment of adjusting the arrangement of elements that form the device in order to minimize optical signal loss in the transmitting or receiving process. 
     Such alignments may include passive alignments and active alignments. A passive alignment is an alignment method of fixating each element of a multi-channel optical module at predetermined positions on a substrate, whereas an active alignment is an alignment method of aligning each element of a multi-channel optical module to find a point where the efficiency of an optical signal being transmitted or received is the highest by auto or manual operation of an alignment equipment, laser welding equipment, etc, in consideration of the strength and weakness of the optical signal, beam pattern, and method of transmitting or receiving the optical signal. 
     The passive alignment costs less since the alignment method and packaging of each element is simple, but is less precise and reliable. On the other hand, the active alignment is very precise and reliable since it considers the optical power, beam pattern, and receiving efficiency of each element, but it takes a great deal of manufacturing time and cost. 
     SUMMARY 
     Therefore, a purpose of various embodiments of the present disclosure is to provide a multi-channel optical module capable of minimizing optical signal loss and reducing the manufacturing cost, and a manufacturing method thereof 
     Another purpose of the various embodiments of the present disclosure is to provide a multi-channel optical module capable of minimizing the coupling loss caused by distances between components and alignment errors. 
     In an embodiment, there is provided multi-channel optical module including: a multi-channel optical fiber block configured to transmit an optical signal; a submount comprising an array optical receiving element unit configured to receive the optical signal; and a mirror unit arranged on a metal optical bench and configured to induce the optical signal transmitted from the multi-channel optical fiber block to the array optical receiving element unit, wherein for the inducement of the optical signal to the array optical receiving element unit, the mirror unit is passively aligned with the array optical receiving element unit, and the multi-channel optical fiber block is actively aligned with the mirror unit. 
     In the embodiment, the passive alignment may be performed by visually confirming a proceeding path of visible light. 
     In the embodiment, one side of the metal optical bench may be depressed towards its inside, and a submount may be arranged on the depressed part of the metal optical bench. 
     In the embodiment, a thickness of the metal optical bench may correspond to a focal distance of the second array lens, a thickness of a submount, and a thickness of the array optical receiving element unit. 
     In the embodiment, the device may further include a housing bottom where the submount and the metal optical bench are mounted. 
     In the embodiment, the multi-channel optical fiber block may be mounted on the housing bottom. 
     In the embodiment, the mirror unit includes an incidence surface through which the optical signal enters the mirror unit; a reflective surface where the optical signal that entered through the incidence surface is totally reflected; and an exit surface from which the totally reflected optical signal exits towards the array optical receiving element unit. 
     In the embodiment, the mirror unit may be formed by bonding a first mirror piece having a reflective surface of 45°; and a second mirror piece having a reflective surface of 45°. 
     In the embodiment, the mirror unit may further include a first array lens formed on the incidence surface; and a second array lens formed on the exit surface, wherein the optical signal may enter the incidence surface through the first array lens, and may exit the second array lens through the exit surface. 
     In the embodiment, for the inducement of the optical signal from the first array lens to the second array lens, the first array lens and the second array lens may be passively aligned to each other. 
     In the embodiment, the passive alignment may be performed by visually confirming a proceeding path of visible light. 
     In the embodiment, the reflective surface may be coated with a high reflective dielectric material in a wavelength that totally reflects the optical signal. 
     In the embodiment, at least a part of the visible light may penetrate the reflective surface and proceed. 
     In another embodiment, there is provided a method for manufacturing a multi-channel optical module including forming a mirror unit by passively aligning a first array lens and a second array lens to each other such that an optical signal that enters from the first array lens formed on an incidence surface of a mirror reaches to the second array lens formed on an exit surface of the mirror; passively aligning the mirror unit to an array optical receiving element unit such that the optical signal that exits the second array lens reaches a predetermined position of the array optical receiving element unit; and actively aligning a multi-channel array optical fiber block configured to transmit the optical signal to the first array lens of the mirror unit using the optical signal such that the optical signal reaches the array optical receiving element. 
     In the embodiment, the array optical receiving element unit on a submount may be placed on one side of a metal optical bench depressed towards the inside, and the mirror unit may be arranged and fixed on the metal optical bench. 
     In the embodiment, the passive alignment of the first array lens and the second array lens and the passive alignment of the mirror unit and the array optical receiving element unit may be performed by visually confirming a proceeding path of visible light. 
     In the embodiment, a thickness of the metal optical bench may be formed to correspond to a focal distance of the second array lens, a thickness of the submount and a thickness of the array optical receiving element unit. 
     According to the aforementioned various embodiments, there is provided a multi-channel optical module wherein an optical coupling efficiency between elements have been improved by combining passive alignment and active alignment. 
     Furthermore by combining the passive alignment and active alignment, it is possible to precisely align elements of the multi-channel optical module, minimize optical signal loss, and reduce the manufacturing cost of the multi-channel optical module. 
     Furthermore, it is possible to apply the multi-channel optical module to single mode signal transmission for high speed long distance data transmission of massive data. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings; however, they may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the example embodiments to those skilled in the art. 
       In the drawing figures, dimensions may be exaggerated for clarity of illustration. It will be understood that when an element is referred to as being “between” two elements, it can be the only element between the two elements, or one or more intervening elements may also be present. Like reference numerals refer to like elements throughout. 
         FIG. 1  is a perspective view illustrating a submount configuration of a multi-channel optical module, according to an embodiment of the present disclosure; 
       FIG. 2  is a perspective view illustrating a method for arranging the submount illustrated in  FIG. 1  together with a metal optical bench; 
         FIG. 3  is a side view illustrating a method for forming a mirror having a reflective surface of 45°; 
         FIG. 4  is a side view illustrating in detail a configuration of the mirror of  FIG. 3 ; 
         FIG. 5  is a perspective view illustrating a method for forming and aligning a mirror on the submount and metal optical bench illustrated in  FIG. 2 ; 
         FIG. 6  is a perspective view illustrating a final configuration of a multi-channel optical module according to an embodiment of the present disclosure; and 
         FIG. 7  is a flowchart schematically illustrating a method for manufacturing a multi-channel optical module according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments will be described in greater detail with reference to the accompanying drawings. Embodiments are described herein with reference to cross-sectional illustrations that are schematic illustrations of embodiments (and intermediate structures). As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments should not be construed as limited to the particular shapes of regions illustrated herein but may include deviations in shapes that result, for example, from manufacturing. In the drawings, lengths and sizes of layers and regions may be exaggerated for clarity. Like reference numerals in the drawings denote like elements. 
     Terms such as ‘first’ and ‘second’ may be used to describe various components, but they should not limit the various components. Those terms are only used for the purpose of differentiating a component from other components. For example, a first component may be referred to as a second component, and a second component may be referred to as a first component and so forth without departing from the spirit and scope of the present disclosure. Furthermore, ‘and/or’ may include any one of or a combination of the components mentioned. 
     Furthermore, a singular form may include a plural from as long as it is not specifically mentioned in a sentence. Furthermore, “include/comprise” or “including/comprising” used in the specification represents that one or more components, steps, operations, and elements exist or are added. 
     Furthermore, unless defined otherwise, all the terms used in this specification including technical and scientific terms have the same meanings as would be generally understood by those skilled in the related art. The terms defined in generally used dictionaries should be construed as having the same meanings as would be construed in the context of the related art, and unless clearly defined otherwise in this specification, should not be construed as having idealistic or overly formal meanings. 
     It is also noted that in this specification, “connected/coupled” refers to one component not only directly coupling another component but also indirectly coupling another component through an intermediate component. On the other hand, “directly connected/directly coupled” refers to one component directly coupling another component without an intermediate component. 
     Examples of internal optical coupling methods for an optical receiving module (or optical transmitting module) that is a type of multi-channel optical module include a method for directly coupling an optical receiving element to a multi-channel optical fiber connector having a mirror with an predetermined incident angle (for example, 45°), a method for coupling an optical receiving element having a mirror with a predetermined incident angle to a polymer optical waveguide and connecting the polymer optical waveguide to a multi-channel optical fiber connector; a method for coupling an optical receiving element to a polymer optical waveguide perpendicularly and connecting the polymer optical waveguide to a multi-channel optical fiber connector, and a method of coupling an optical receiving element fixated to a plastic package perpendicularly to a multi-channel optical connector. 
     Of the aforementioned methods, in the method of coupling an optical receiving element to a polymer optical waveguide having a mirror with a predetermined incident angle (for example, 45°) and the connecting the polymer optical waveguide to a multi-channel optical fiber connector, it is easy to form the mirror, and it is possible to embed an optical coupler, optical switch, and WDM (Wavelength Division Multiplexing) element and the like in the polymer optical waveguide, and thus it is advantageous in terms of expandability. 
     Of the aforementioned methods, the method for coupling an optical receiving element to a polymer optical waveguide having a mirror of a predetermined incident angle (for example, 45°) and connecting a polymer optical waveguide to a multi-channel optical fiber connector is advantageous in terms of expandability, since it is relatively easy to form a mirror and embed an optical coupler, optical switch, and WDM (Wavelength Division Multiplexing) element and the like to the polymer optical waveguide. 
     However, in such an optical receiving module having a two dimensional optical coupling structure, there occurs much coupling loss due to a distance between the multi-channel optical fiber and optical detector, thereby not providing sufficient efficiency. 
     Hereinafter, explanation will be made on manufacturing a multi-channel optical receiving module by combining the active alignment method with the passive alignment method, thereby the adopting the active alignment method minimizing the coupling loss between elements and ultimately improving the optical coupling efficiency of the multi-channel optical receiving module. Furthermore, the adopting the passive alignment method makes it possible to reduce the packaging-cost for manufacturing the multi-channel optical receiving module. 
     Meanwhile, in the present embodiment, a multi-channel optical receiving module is explained as an example of the multi-channel optical module, but it would be obvious to those skilled in the art that there is no limitation thereto. For example, the embodiments of the present disclosure wherein the passive alignment and active alignment are combined and used can be easily applied to an optical transmitting module as well. 
     The multi-channel optical module that will be explained hereinafter is a multi-channel optical transmitting module or optical receiving module integrated with surface emitting laser diodes or surface receiving photo detectors and applied to optical transceiver and highly integrated multifunctional optical sub module platform for use in access networks based on a next generation WDM or TDM (Time Division Multiplexer) providing an optical internet service of 10 gigabyte or more. 
       FIG. 1  is a perspective view illustrating a submount of a multi-channel optical module according to an embodiment of the present disclosure. With reference to  FIG. 1 , on a submount  110  of a multi-channel optical module  100 , an array IC unit  120  and array optical receiving element unit  130  are mounted. 
     The array IC unit  120  may be an array TIA (trans-impedance amplifier) connected to an FPCB  10  by wire bonding  121 . 
     Although not illustrated in the figures, a DC electrode of the array IC unit  120  may be connected to the FPCB  10  by wire bonding through a transmission line (hereinafter referred to as a transmission path) formed on the submount  110 . 
     The array optical receiving element unit  130  includes a plurality of optical receiving elements in the form of an array. The plurality of optical receiving elements are monolithically integrated in the array optical receiving element unit  130 , and the optical receiving elements may be for example photodiodes. The array optical receiving element unit  130  is electrically connected to the array IC unit  120  through wire bonding  122 . 
     The array IC unit  120  and array optical receiving element unit  130  are mounted on the submount  110 . In an embodiment, the FPCB  10  may be mounted on the submount  110 . 
     Meanwhile, herein, only the array IC unit  120 , array optical receiving element unit  130  and FPCB  10  were exemplified as the components of the submount  110 , but there is no limitation thereto, and thus, the submount  110  may further include other components well known in the field. 
       FIG. 2  is a perspective view illustrating a method of arranging the submount illustrated in  FIG. 1  together with a metal optical bench. With reference to  FIG. 2 , the submount  110  of  FIG. 1  is arranged on a housing bottom  20  together with the metal optical bench  140 . 
     The metal optical bench  140  has a structure wherein one side is depressed and mounted on the housing bottom  20 . In an embodiment, the metal optical bench  140  may have a structure of ‘ ’ form with one side depressed. 
     The submount  110  is mounted on the housing bottom  20  and arranged on the depressed part of the metal optical bench  140 . 
     In  FIG. 2 , the thickness of the metal optical bench  140  is more than the thickness of the submount  110 . In an embodiment, the thickness of the metal optical bench  140  may be determined with reference to sum of a focal distance of the array lens  154  (see  FIG. 4 ), the thickness of the optical receiving element on the submount  110 , and the thickness of the submount  110 . 
     In an embodiment, the housing bottom  20  may be a bottom  20  of an XMD MSA (Multi-Source Agreement) form-factor. 
       FIG. 3  and  FIG. 4  are side views illustrating in detail a mirror. With reference to  FIG. 3 , the mirror  150  may be formed by bonding a first mirror piece  151  and a second mirror piece  152 . The first mirror piece  151  has a reflective surface A coated with a high reflective dielectric material, incidence surface B, and exit surface C coated with an anti-reflective material. The second mirror piece  152  has an incidence surface D, an exit surface E, and a reflective surface A. Herein, the reflective surfaces A of the mirrors may be the reflective surfaces having an incident angle of 45° as illustrated in  FIG. 3 . Unlike the first mirror piece  151 , the second mirror piece  152  may not be coated with a high reflective material and an anti-reflective material. In an embodiment, the mirror  150  may have a cubic form made by bonding the first mirror piece  151  and second mirror piece  152 . 
     The mirror  150  includes the reflective surface A having a predetermined incident angle inside thereof In an embodiment, the predetermined incident angle may be 45°. 
     The reflective surface A of the mirror  150  is coated with a material that totally reflects only a certain wavelength band of an optical signal. In an embodiment, the material coated on the reflective surface A may be a high reflective (HR) dielectric material that totally reflects a wavelength of 1330 nm or 1550 nm used in optical communication. 
     Meanwhile, the incidence surface B and exit surface C of the mirror  150  are coated with an anti-reflective material. In  FIG. 3 , the incidence surface B of the mirror  150  is a left side surface of the mirror  150  where an optical signal or visible light enters, and the exit surface C is a bottom surface that faces the array optical receiving element unit  130  where an optical signal or visible light exits from the mirror  150  and enters the array optical receiving element unit  130 . 
     With reference to  FIG. 4 , the mirror  150  includes a first mirror piece  151 , second mirror piece  152 , and array lens  153 ,  154 . 
     The mirror  150  is configured such that an optical signal entering to the incidence surface B enters as a parallel light to the reflective surface A with an angle of 45° and is totally reflected by the reflective surface A with an angle of 45°, and exits through the exit surface C. 
     On the contrary, if a visible light enters to the incidence surface B and enters to the reflective surface A as a parallel light with an angle of 45°, some of the visible light is reflected and exits through the exist surface C and another is penetrated through the reflective surface A and exits through the exit surface E due to the high reflective dielectric material coated on the reflective surface A. Furthermore, if a visible light enters to the incidence surface D and enters to the reflective surface A, some of the visible light is reflected by the reflective surface A and exits through the exit surface E, and another is penetrated through the reflective surface A and exits through the exit surface C. For this purpose, the first mirror piece  151  and the second mirror piece  152  having an incident angle of 45° are bonded together to form the mirror  150  of a cubic form. 
     The part of the first mirror piece  151  and the second mirror piece  152  that contact each other form the reflective surface A. The left surface of the first mirror piece  151  is the incidence surface B where an array lens  153  is formed. The bottom surface of the first mirror piece  151  is an exit surface C where another array lens  154  is formed. 
     As explained above, the light source (optical signal) enters to the incidence surface B through the array lens  153 , and then reflected by the reflective surface A, and then exits to the array lens  154  through the exit surface C. 
     For this purpose, the reflective surface A of the mirror  150  may be configured such that it is coated with a high reflective dielectric material, and that has an incident angle of 45°. For example, regarding the internal reflectivity characteristics in a case where the incident angle of the reflective surface A is 45°, when a parallel light that is parallel to the housing bottom  20  enters, the reflective surface A satisfies the total reflection conditions of the Snell&#39;s Law n 1 sin θ1=n2 sin θ2, and thus light of all wavelengths proceed towards the exit surface C. However, the reflective surface A having an incident angle of 45° may be coated with a high reflective dielectric material of a wavelength corresponding to the optical signal to totally reflect the optical signal, to reflect some of the visible light, and to penetrate another visible light, thereby facilitating the path. For example, the optical signal may be an optical signal of a long wavelength used in optical communication, that is, a wavelength of c-band or L-band (ex. 1310 nm, 1550 nm or 1625 nm). 
     Meanwhile, the mirror  150  is configured such that some of visible light in the wavelength is reflected by the reflective surface A, while some other of visible light in wavelength is penetrated through the reflective surface A and the second mirror piece  152 , and the optical signal is totally reflected by the reflective surface A and exited through the exit surface C. Accordingly, the visible light being penetrated make it possible to passive align the array lens  153  of the incidence surface B and the array lens  154  of the exit surface C by visual observation. 
     Herein, the array lens  153  of the incidence surface B and the array lens  154  of the exit surface C are the same collimate lens, and they may be passively aligned such that they correspond to each other regardless of order and be bonded to the mirror  150 . 
     For example, the array lens  153  is bonded to the center of the incidence surface B, and the visible light enters to the incidence surface B. Some of entered light is reflected by the reflective surface A, and the location of the array lens  153  is confirmed visually precisely using the light that proceeded to the exit surface C. Therefore, the array lens  153  of the incidence surface B may be mounted precisely such that the optical signal that entered the array lens  153  reaches the array lens  154  of the exit surface C. 
     In an embodiment, the array lens  153 ,  154  are each configured to include the same number of lens as the number of channels of the entering optical signals or the number of channels of the array optical receiving element unit  130 . For example, when the number of channels of the entering optical signals or the array optical receiving elements unit  130  is four, the number of lens that the array lens  153 ,  154  each includes may be four. 
     Meanwhile, explanation on the passive alignment and mounting of the mirror  150  on the metal optical bench  140  such that the optical signals exiting through the array lens  154  reach the exact position of the array optical receiving element unit  130  will be explained with reference to  FIG. 5 . 
       FIG. 5  is a perspective view of a method for forming and aligning a mirror on the metal optical bench and above the submount illustrated in  FIG. 2 . Referring to  FIG. 5 , the multi-channel optical module  100  forms the mirror  150  on the metal optical bench  140 . 
     The mirror  150  is formed on the metal optical bench  140  and it is aligned with the array optical receiving element unit  130  using the passive alignment method. That is, the mirror  150  mounted on the metal optical bench  140  is passively aligned with array optical receiving element unit  130  by visual method such that some of the visible light in the wavelength band entering to the incidence surface D penetrates the reflective surface A and exits through the array lens  154  integrated on the exit surface C, and reaches to the optical receiving elements of the array optical receiving element unit  130  on the submount  110 . 
     In an embodiment, the aforementioned passive alignment uses the characteristics of the visible light entering the incidence surface D, and being penetrated through the reflective surface A, and reaching to the array optical receiving element unit  130  through the exit surface C. 
     Meanwhile, the mirror  150  further includes array lens  153 ,  154  each formed on the incidence surface B and exit surface C. First of all, an optical signal entering the mirror  150  enters the incidence surface B through the array lens  153 , and is then totally reflected by the reflective surface A, thereby changing the proceeding path downward, and then exists the array lens  154  through the exit surface C until it reaches the array optical receiving element unit  130 . 
       FIG. 6  is a perspective view of a final configuration of the multi-channel optical module according to an embodiment of the present disclosure. With reference to  FIG. 6 , with the submount  110 , metal optical bench  140 , and mirror  150  of  FIG. 5 , the multi-channel array optical fiber block  160  is mounted on the multi-channel optical module, ultimately completing the multi-channel optical module  100 . 
     Meanwhile, in  FIG. 6 , it is illustrated that the multi-channel array optical fiber block  160  is mounted on the housing bottom  20 , but there is no limitation thereto. For example, the multi-channel array optical fiber block  160  may be mounted on the metal optical bench  140  instead of the housing bottom  20 . 
     In  FIG. 6 , the multi-channel array optical fiber block  160  is arranged and aligned in a three-dimensional active alignment method. As the optical signal  30  transmitted through the array optical fiber of the multi-channel array optical fiber block  160  enters the array lens  153  of the incidence surface B, and then exits the array lens  154  of the exit surface C, and then actively aligned such that the optical efficiency of the optical signal entering the array optical receiving element unit  130  mounted on the submount  110  reaches the maximum level, a final multi-channel optical module  100  is manufactured. Herein, as illustrated in  FIG. 6 , using the metal optical bench  140  wherein one side is depressed and the mirror  150  having a cubic form, it is possible to actively align the multi-channel array optical fiber block  160  and the array optical receiving element unit  130 . The technical means of the three dimensional active alignment of finding a point where the efficiency of optical signal received or transmitted through automatic or manually operated alignment equipment, laser welding equipment, etc, is the maximum value in consideration of the strength and weakness of the optical signal, and optical signal transmitting or receiving method is well known, and thus detailed explanation is omitted herein. 
     According to the aforementioned configurations, a multi-channel optical module is provided where an optical coupling efficiency between elements is improved using both a passive alignment and active alignment. Such a multi-channel optical module is applicable to a single mode signal transmission for a large volume high speed long distance data transmission. 
     Furthermore, by combining the passive alignment and active alignment method and then using the same, it is possible to align each element of the multi-channel optical module precisely, and accordingly, optical signal loss is minimized. Furthermore, by partially utilizing the passive alignment, the overall manufacturing cost of the multi-channel optical module is relatively reduced. 
     For example, unless the invention disclosed in the present specification is used, mounting or forming each of the multi-channel array optical fiber block  160 , array lens  153 ,  154 , and array optical receiving element unit  130  has to depend on the three dimensional active alignment, which would lead to significant optical coupling loss, and increase of packaging cost. On the other hand, according to the invention disclosed in the present specification, since the multi-channel optical module is manufactured using the two dimensional passive alignment method and three dimensional active alignment method together, it is possible to improve the optical coupling efficiency, and mass production, and further, it is possible to achieve price reduction due to the improvement of yield and reliability, and the reduction of packaging time. 
       FIG. 7  is a flowchart schematically illustrating a method for manufacturing a multi-channel optical module according to an embodiment of the present specification. With reference to  FIG. 7 , the method for manufacturing the multi-channel optical module includes step S 110  to step S 160 . 
     At step S 110 , the array optical receiving element unit  130  (see  FIG. 1 ) and IC  120  (see  FIG. 1 ) and FPCB  10  (see  FIG. 1 ) are mounted on the submount ( 110 , see  FIG. 1 ) to form a submount unit. The submount unit refers to a component that includes an array optical receiving element unit  130 , IC  120 , or FPCB  10 . 
     At S 120 , a metal optical bench  140  (see  FIG. 2 ) and submount  110  (see  FIG. 2 ) are formed on the housing bottom  20  (see  FIG. 2 ). 
     At S 130 , the first mirror piece  151  (see  FIG. 3 ) and the second mirror piece  152  ( FIG. 3 ) are bonded to each other to form the mirror  150  (see  FIG. 3 ). The mirror  150  refers to a component that includes the first mirror piece  151  and second mirror piece  152 . 
     At S 140 , the first array lens  153  (see  FIG. 4 ) formed on the incidence surface B (see  FIG. 4 ) of the mirror  150  (see  FIG. 4 ) and the second array lens  154  (see  FIG. 4 ) formed on the exit surface C (see  FIG. 4 ) are passively aligned to form the mirror unit. The mirror unit refers to a component that includes a first array lens  153 , second array lens  154 , and mirror  150 . 
     In an embodiment, the passive alignment of the first array lens  153  and second array lens  154  may be a passive alignment that is performed visually using the visible light. 
     At S 150 , in order to have the optical signal  30  (see  FIG. 6 ) exiting the second array lens  154  to reach an exact position of the array optical receiving element unit  130 , the mirror unit is arranged and fixed on the metal optical bench  140  ( FIG. 5 ) such that the second array lens  154  is passively aligned with the array optical receiving element unit  130  on the submount  110  (see  FIG. 5 ). 
     Herein, the metal optical bench  140  may be configured such that one side is depressed, and the submount  110  may be placed on the depressed part of the metal optical bench  140 . 
     In an embodiment, the passive alignment between the mirror  150  and the array optical receiving element unit  130  may be a passive alignment being performed visually using visible light. 
     At S 160 , the multi-channel array optical block  160  is actively aligned with the array receiving element unit  130  using the optical signal  30  (see  FIG. 6 ) light entering from the multi-channel array optical fiber block  160  (see  FIG. 6 ) to the first array lens  153  and exiting the second array lens  154  so as to complete the final multi-channel optical module  100  (see  FIG. 6 ). 
     Meanwhile, further explanation on the passive alignment and active alignment not explained herein is the same as mentioned above. 
     Example embodiments have been disclosed herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. In some instances, as would be apparent to one of ordinary skill in the art as of the filing of the present application, features, characteristics, and/or elements described in connection with a particular embodiment may be used singly or in combination with features, characteristics, and/or elements described in connection with other embodiments unless otherwise specifically indicated. Accordingly, it will be understood by those of skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims.