Multi-channel receiver optical sub-assembly and manufacturing method thereof

Provided herein are a multi-channel receiver optical sub-assembly and a manufacturing method thereof. The multi-channel receiver optical sub-assembly includes a PLC chip having a first side into which an optical signal is received and a second side from which the received signal is outputted, with an inclined surface formed on the second side of the PLC chip at a preset angle, a PD carrier bonded onto the PLC chip and made of a glass material, and an SI-PD bonded onto the PD carrier, a lens being integrated therein. The PLC chip, the PD carrier, and the SI-PD are passively aligned by at least one alignment mark and then are bonded.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean patent application number 10-2015-0160635 filed on Nov. 16, 2015, the entire disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND

Field of Invention

Various embodiments of the present disclosure relate to a multi-channel receiver optical sub-assembly and a manufacturing method thereof.

Description of Related Art

As broadband mobiles, clouding networks, IPTVs and smart-phones are spreaded, video-based high-capacity communications are explosively increased. Thus, a transmission rate of an optical module is dramatically increased, and simultaneously, there is an urgent need for technology that may implement a receiver optical sub-assembly in a very small size and at a low cost.

Generally, when the receiver optical sub-assembly uses an AWG (Arrayed Waveguide Grating) PLC (Planar Lightwave Circuit) chip having a function of wavelength multiplexing filter, or a PLC chip on which a multi-channel straight waveguide is formed, first, one end of the PLC chip is vertically 90° polished so as to implement a light receiving part on one end of the PLC chip. Subsequently, an SI-PD (Surface-Illuminated Photo Diode) on which the lens is not integrated is precisely flip-chip bonded to a top of a PD (Photo Diode) carrier.

Therefore, in order to effectively couple an optical signal outputted from the PLC chip with the SI-PD, the PLC chip that is vertically polished at one end thereof and the PD carrier on which the SI-PD is integrated are arranged to face each other. In this state, a bulky glass lens is inserted between the PLC chip and the SI-PD so that the PLC chip and the SI-PD are horizontally arranged. Thereafter, active alignment and butt-coupling should be performed between the PLC chip and the SI-PD.

In the case of an SI-PD for optical communication of 25 Gbps or more, the diameter of a light receiving part of the SI-PD is very small, that is, about 20 um, so that it is very difficult to passively align the SI-PD with the PLC chip. That is, in the case where the SI-PD, the glass lens, and the PLC chip are discretely passively aligned with each other, if the misalignment of about 10 um occurs for the narrow light receiving part of the SI-PD, optical coupling efficiency between the SI-PD and the PLC chip is remarkably lowered. Therefore, the PLC and the SI-PD should be actively aligned with each other.

Accordingly, if the PLC chip and the SI-PD are actively aligned with each other, the lens is disposed between the SI-PD and the PLC chip as described above, so as to enhance optical coupling efficiency and a yield. In this respect, since the conventional light receiving part should use a glass lens with a large size, the length of the light receiving part is increased. Further, after the PLC chip, the lens, and the SI-PD are discretely arranged, they should be actively aligned and assembled with each other. Thus, a process is complicated and a long time is required, so that it is difficult to achieve a reduction in cost of the receiver optical sub-assembly.

In the conventional receiver optical sub-assembly, the SI-PD is disposed on a side of the PD carrier, and a TIA array amplifying a photo-current, outputted from the SI-PD, to a high voltage is disposed on a top of the PD carrier. Therefore, a high frequency transmission line between the SI-PD and the TIA array is bent at 90°. At this time, if a high speed signal of 25 Gbps or more passes through the high frequency transmission line that is bent at 90°, severe impedance mismatch occurs and a high frequency signal is radiated, so that the performance of the receiver optical sub-assembly is considerably deteriorated.

Consequently, in the related art, when the receiver optical sub-assembly of 25 Gbps or more is mass-produced, production yield is reduced in terms of high frequency characteristics, thus making it very difficult to achieve a reduction in cost of the receiver optical sub-assembly. Particularly, in a receiver optical sub-assembly of 40 Gbps or more, deterioration in high frequency characteristics becomes more serious. Therefore, in the related art, another structure should be applied to the receiver optical sub-assembly of 40 Gbps or more. As a result, it is impossible to use the conventional receiver optical sub-assembly as a universal structure of a receiver optical sub-assembly for a high frequency.

SUMMARY

Various embodiments of the present disclosure are directed to a multi-channel receiver optical sub-assembly (ROSA) implemented by passive alignment and a manufacturing method thereof.

The present disclosure provides a multi-channel receiver optical sub-assembly including a PLC chip having a first side into which an optical signal is received and a second side from which the received signal is outputted, with an inclined surface formed on the second side of the PLC chip at a preset angle; a PD carrier bonded onto the PLC chip and made of a glass material; and an SI-PD bonded onto the PD carrier, a lens being integrated therein, wherein the PLC chip, the PD carrier, and the SI-PD may be passively aligned by at least one alignment mark and then may be bonded.

Furthermore, the present disclosure provides a method of manufacturing a multi-channel receiver optical sub-assembly, including forming an inclined surface at a preset angle on a side of a PLC chip from which an optical signal is outputted; passively aligning and bonding an SI-PD onto a PD carrier of a glass material, a lens being integrated onto a bottom surface of the SI-PD; and passively aligning and bonding the PD carrier onto the PLC chip, wherein the PLC chip, the PD carrier and the SI-PD may be passively aligned and bonded by at least one alignment mark.

DETAILED DESCRIPTION

When it is determined that the detailed description of the related art may obscure the gist of the present invention, the detailed description thereof will be omitted herein.

It should be understood 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.

Further, “include” or “may include” used in the specification represents that one or more components, steps, operations, and elements exist or are added. Furthermore, “include” or “have” used in the specification is only used for the purpose of representing features, figures, steps, operations, components, parts or combinations described in the specification, but should not be construed as limiting the existence or addition of one or more other features, figures, steps, operations, components, parts or combinations thereof.

A singular form may include a plural from as long as it is not specifically mentioned in a sentence.

Hereinafter, embodiments will be described in greater detail with reference to the accompanying drawings.

FIG. 1is a view illustrating a structure of a multi-channel receiver optical sub-assembly using an AWG PLC chip according to a first embodiment of the present disclosure, andFIG. 2is a view illustrating a structure of a multi-channel receiver optical sub-assembly using a multi-channel linear waveguide PLC chip according to a second embodiment of the present disclosure.

Since a general structure of a multi-channel receiver optical sub-assembly200according to the second embodiment of this disclosure illustrated inFIG. 2remains the same as the first embodiment of this disclosure except for the kind of a PLC chip210, the structure of the multi-channel receiver optical sub-assembly100according to this disclosure will be described below with reference to the embodiment ofFIG. 1.

Referring toFIG. 1, the multi-channel receiver optical sub-assembly100according to the first embodiment of the present disclosure may include a PLC chip110, a PD carrier120, and an SI-PD130.

The PLC chip110may be an AWG PLC chip with a function of a wavelength multiplexing filter. As described above, in the second embodiment of this disclosure, the PLC chip210may be a multi-channel straight waveguide PLC chip.

A multi-channel optical waveguide111may be formed on the PLC chip110, and a material of the optical waveguide may be silica, polymer, silicone and the like.

One side of the PLC chip110is coupled with an optical fiber. As illustrated inFIG. 1, when the PLC chip110is the AWG PLC chip, a single channel optical fiber is coupled with the PLC chip110through a lens, and a single channel optical fiber block may be coupled with the PLC chip110through pig-tailing. When the PLC chip110is the multi-channel straight waveguide PLC chip as illustrated inFIG. 2, the multi-channel optical fiber block may be coupled with the PLC chip110through pig-tailing.

An optical signal incident into the PLC chip110from the optical fiber may be traveled (propagated) along the optical waveguide111to the other side of the PLC chip110.

As illustrated inFIGS. 3 and 4, the other side of the PLC chip110is formed as an inclined surface112having a preset inclination angle with respect to a bottom surface of the PLC chip110. In various embodiments of the present disclosure, the inclination angle may be 45°, and the inclined surface112may be formed by a polishing or etching process. As illustrated inFIG. 4, the optical signal reaching the other side of the PLC chip110along the optical waveguide111is reflected from the inclined surface112, and then a travel direction thereof is bent at 90°. Thus, the optical signal propagated horizontally along the top surface of the PLC chip110is vertically reflected while passing through the inclined surface112.

In an embodiment, a metal coated layer113may be formed on the inclined surface. The metal coated layer113may be composed of Cr/Au, Cr/Ni/Au, Ti/Pt/Au or the like. The metal coated layer113may act as a reflection mirror that minimizes the scattering of the optical signal reflected from the inclined surface112, by maximizing the reflection efficiency of the optical signal.

The above-mentioned structure of the PLC chip110allows the multi-channel receiver optical sub-assembly100according to the present disclosure to change an optical path without using a high frequency transmission line bent at 90° as in the related art, thus minimizing an optical coupling loss between the PLC chip100and an SI-PD130that will be described below without deteriorating the high frequency characteristics. Thus, the receiver optical sub-assembly according to this disclosure may provide optimized high frequency characteristics to a receiver optical sub-assembly of 25 Gbps or more.

The PD carrier120is bonded to the top surface of the PLC chip110. In various embodiments of the present disclosure, the PD carrier120may be formed of a flat glass material that may transmit light without a loss. To be more specific, the PD carrier120may be formed from Quartz, sodalime glass, BK7 glass or the like having excellent light transmittance. In various embodiments, the thickness of the glass material forming the PD carrier120may range from 100 to 150 um.

The PD carrier120is secured to the top surface of the PLC chip110by passive alignment and epoxy bonding. As illustrated inFIG. 3, the PD carrier120may be bonded to a region of the top surface of the PLC chip110on which the inclined surface112is formed. Epoxy applied to the top surface of the PLC chip110and the PD carrier120is excellent in light transmittance, and should have index matching characteristics that are similar to the glass material forming the optical waveguide111and the PD carrier120. Therefore, epoxy may be named as index matching epoxy.

In various embodiments, the SI-PD130into which a lens131that will be described later has been integrated is first bonded to the PD carrier120, and the PD carrier120to which the SI-PD130has been bonded may be bonded to the PLC chip110. A method of passively aligning the PLC chip110with the PD carrier120will be described below in detail.

The optical signal that is reflected from the inclined surface112of the PLC chip110and then is vertically outputted is diverged while passing through a clad layer of the optical waveguide111, the epoxy of the PD carrier120, and the PD carrier120.

Generally, if a vertical surface is formed on the other side of the PLC chip110, it is problematic in that the horizontally propagated optical signal is reflected from the vertical surface and then is coupled to and fed back to the optical waveguide111. However, in the multi-channel receiver optical sub-assembly100according to this disclosure, the optical signal is reflected from the inclined surface112, is vertically propagated, and is diverged while passing through the PD carrier120. Thus, the optical signal reflected from an upper surface of the PD carrier120is not reversely coupled with the optical waveguide111.

Therefore, in the multi-channel receiver optical sub-assembly100according to this disclosure, AR coating is not required on the surfaces of the PLC chip110and the PD carrier120, so that a processing cost is reduced.

The SI-PD130is bonded to the top surface of the PD carrier120. In various embodiments of the disclosure, the SI-PD130may be a PIN-PD (PIN Photo-Diode) or an Avalanche PD (Avalanche Photo-Diode; APD). The SI-PD130is fixed to the top surface of the PD carrier120by passive alignment and flip-chip bonding. According to an embodiment, if the SI-PD130is a discrete chip type, the SI-PD130may be fixed by flip-chip bonding. If the SI-PD130is an array chip type, the SI-PD130may be fixed by die bonding or flip-chip bonding. A method of passively aligning the PD carrier120with the SI-PD130into which the lens131is integrated will be described below in detail.

In various embodiments of this disclosure, the lens131is integrated into the bottom surface of the SI-PD130, as illustrated inFIG. 4. The lens131plays an important role in optical coupling efficiency of the PLC chip110with the SI-PD130. Therefore, the lens131should be precisely monolithic-integrated into the SI-PD130.

In this disclosure, when the lens131is monolithic-integrated into the SI-PD130, the refractive index of the SI-PD130into which the lens131is integrated is about 3.2 and high, so that it is possible to form the lens131with a small radius of curvature. Further, the lens131with a small radius of curvature may be easily arranged with the precision of about 1 um using a photomask contact aligner that is employed during a semiconductor process. Therefore, according to this disclosure, the photomask contact aligner is employed during the manufacture of the SI-PD130, thus allowing the lens131to be easily passively aligned with and integrated into the SI-PD130.

In various embodiments of this disclosure, AR coating may be applied to a surface of the lens131integrated into the bottom surface of the SI-PD130. The AR coating prevents the module characteristics of the multi-channel receiver optical sub-assembly100from being deteriorated by optical reflection. The AR coating process is a routine process for manufacturing the SI-PD130. Thus, when the multi-channel receiver optical sub-assembly100according to this disclosure is manufactured, manufacturing cost is not increased by the AR coating on the surface of the lens131.

As illustrated inFIGS. 3 and 4, a first SLC (Single Layer Capacitor)140may be further bonded to the top surface of the PD carrier120to be adjacent to the SI-PD130, thus removing a power supply noise of the SI-PD130.

The PLC chip110, the PD carrier120, and the SI-PD130may be mounted on a first metal optical bench (Metal Optical Bench; MOB)150. A second metal optical bench160may be mounted on the first metal optical bench150to be adjacent to the inclined surface112of the PLC chip110. In order to electrically insulate the first metal optical bench150from the second metal optical bench160, a (high resistance) submount having high specific resistance may be inserted between the first metal optical bench150and the second metal optical bench160.

In the multi-channel receiver optical sub-assembly100according to this disclosure, the second metal optical bench160serves as an RF GND, and the first metal optical bench150is connected with a metal housing via silver paste. If the first metal optical bench150is electrically connected with the second metal optical bench160, the RF GND is connected with the metal housing. Thus, when the multi-channel receiver optical sub-assembly100is handled, the SI-PD130and a TIA array170are vulnerable to an ESD (electro-static discharge). Therefore, in the multi-channel receiver optical sub-assembly100according to this disclosure, the first metal optical bench150is electrically isolated from the second metal optical bench160by the high resistance submount.

The TIA array170, an RF-FPCB180, and a second SLC190may be further mounted on the second metal optical bench160. The TIA array170converts and amplifies a photocurrent, outputted from the SI-PD130, into high frequency voltage. The RF-FPCB180transmits the high frequency voltage, outputted from the TIA array170, into another device. The second SLC190removes the power supply noise of the TIA array170.

Here, the SI-PD130, the TIA array170, and the RF-FPCB180are arranged to be parallel to each other. As illustrated inFIG. 4, the first metal optical bench150may include a step151in a region on which the second metal optical bench160is mounted so that the SI-PD130provided on the first metal optical bench150is arranged to be parallel with the TIA array170and the RF-FPCB180provided on the second metal optical bench160. Likewise, the second metal optical bench160may also include a step161, as illustrated inFIG. 4, so that the TIA array170and the RF-FPCB180are arranged to be parallel to each other.

Hereinafter, the structure of aligning the PLC chip110, the PD carrier120, and the SI-PD130with each other will be described in detail with reference toFIGS. 5 to 8.

FIG. 5is a view illustrating the structure of the top surface of the PD carrier in the receiver optical sub-assembly according to the present disclosure.

Referring toFIG. 5, the PD carrier120may include on the top surface thereof a plurality of PDC alignment marks121,122and123for performing alignment with the PLC chip110, a flip-chip bonding alignment mark124for performing alignment with the SI-PD130, and solder125. The solder125may be composed of AuSn, AgSn, SnPb or the like. Further, in order to allow the optical signal to be transmitted through the PD carrier120and effectively coupled to the lens131integrated into the bottom surface of the SI-PD130, a metal pattern126that is open to have the same shape as the lens131is formed on an upper portion of the PD carrier120.

The alignment mark may include the PDC longitudinal alignment mark121for performing the longitudinal alignment of the PD carrier120with the PLC chip110. The PDC longitudinal alignment mark121may have various shapes. In an embodiment, as illustrated inFIG. 5, the PDC longitudinal alignment marks may be formed on left and right sides of the PD carrier120at 10 um pattern/distance.

Further, the alignment mark may include a PDC transverse alignment mark122for performing the transverse alignment of the PD carrier120with the optical waveguide111formed on the PLC chip110. The PDC transverse alignment mark122may have various shapes. In an embodiment, as illustrated inFIG. 5, the PDC transverse alignment marks may be formed on four places of the PD carrier120at 10 um pattern/distance.

FIG. 5illustrate an example where cross-shaped PDC transverse/longitudinal alignment marks123are formed on the left and right sides of the PD carrier120to be located between second and third SI-PDs130and PDC transverse alignment marks122. The PD carrier120may be more precisely aligned with the PLC chip110by the PDC transverse/longitudinal alignment marks123.

The flip-chip bonding alignment mark124is formed in a region where the SI-PD130is disposed, and is aligned with an electrode pattern formed on a bottom surface of the SI-PD130to allow the SI-PD130to be correctly bonded to the top surface of the PD carrier120.

A large GND pattern is formed on a remaining top surface where the SI-PD130on the PD carrier120is not bonded to be connected with the GND of the TIA array170, the RF-FPCB180, and the second SLC190.

FIG. 6is a view illustrating a structure in which the SI-PD and the SLC are bonded to the top surface of the PD carrier ofFIG. 5.

The electrode pattern bonded to the flip-chip bonding alignment mark124formed on the top surface of the PD carrier120is formed on the bottom surface of the SI-PD130. The electrode pattern formed on the bottom surface of the SI-PD130and the flip-chip bonding alignment mark124of the PD carrier120are passively aligned with a precision of about 2 to 3 um and then are flip-chip bonded. The misalignment of 2 to 3 um rarely affects optical coupling between the SI-PD130and the PLC chip110.

FIG. 6illustrates an example where four SI-PDs130are flip-chip bonded, respectively, and the flip-chip bonding is applied four times in total. However, in the case of using the array type of SI-PD, die bonding by the passive alignment may be applied instead of the flip-chip bonding or the flip-chip bonding may be applied only once to bond the SI-PD130to the PD carrier120.

In a remaining region in the top surface of the PD carrier120where the SI-PD130is not flip-chip bonded, the GND of the PD carrier120is formed, and the first SLC140for removing the power supply noise of the SI-PD130may be attached to the top of the GND using silver paste.

FIG. 7is a view illustrating the structure in which the PD carrier is bonded to the top surface of the PLC chip in the receiver optical sub-assembly according to the present disclosure.

A plurality of alignment marks114and115may be formed on the top surface of the PLC chip110to perform the alignment with the PD carrier120.

The alignment mark may include the PLC longitudinal alignment mark114that is aligned with the PDC longitudinal alignment mark121formed on the PD carrier120. The PLC longitudinal alignment mark114may have various shapes. In an embodiment, as illustrated inFIG. 7, the PLC longitudinal alignment marks may be formed on left and right sides of the top surface of the PLC chip110at 10 um pattern/distance. The PLC longitudinal alignment mark114is aligned with the PDC longitudinal alignment mark121with the precision of about 5 um. It is possible to check whether they are misaligned or not.

The multi-channel optical waveguide111formed on the top of the PLC chip110is aligned with the PDC transverse alignment marks122formed at 10 um pattern/distance and may be aligned with the precision of 5 um.

FIG. 8illustrates an example where the cross-shaped PLC transverse/longitudinal alignment mark115is formed at a position corresponding to the PDC transverse/longitudinal alignment mark123. The PD carrier120may be more precisely aligned with the PLC chip110by the PLC transverse/longitudinal alignment mark115. The PLC transverse/longitudinal alignment mark115and the PDC transverse/longitudinal alignment mark123are aligned with each other with a precision of about 5 um. It is possible to check whether they are misaligned or not.

The PLC chip110and the PD carrier120may be bonded within a misalignment range of 10 um or less by the passive alignment using the above-described alignment marks and may be bonded by using index matching transparent epoxy.

Referring toFIG. 7, the TIA array170is placed at a distance of 100 um or less from the SI-PD130, thus minimizing the length of the wire bonding. The second SLCs190for removing the power supply noise of the TIA array170are disposed on the upper and lower surfaces of the TIA array170.

FIG. 9is a view illustrating simulation results of optical coupling efficiency between the PD carrier into which the SI-PD is integrated and the PLC chip in the receiver optical sub-assembly according to the present disclosure.

In the simulation ofFIG. 9, the diameter of a light receiving part of the SI-PD130is 24 um, the radius of curvature of the lens131is 105 um, the effective receiving diameter of the lens131is 100 um, and the chip thickness of the SI-PD130is 150 um. The optical waveguide111of the PLC chip110is made of silica, has an index contrast of 2%−Δ, and is 14 um and 2.5 um in width and height, respectively. The refractive index of the PD carrier120is 1.457, and the refractive index of the index matching transparent epoxy used to bond the PD carrier120to the PLC chip110is 1.465.

FIG. 9illustrates the simulation results when the thickness of the PD carrier120is 100 um and 120 um, respectively, and a 3D BPM (beam propagation method) is employed.

As illustrated inFIG. 9, when misalignment between the PD carrier120and the optical waveguide111occurs by +/−18 um, the optical coupling efficiency is 93%, and an optical loss for the maximum optical coupling efficiency (97.5%) is only 0.2 dB.

Meanwhile, when the PLC chip110and the PD carrier120are passively aligned with each other, experiments showed that the occurring misalignment is about 10 to 15 um. That is, it can be seen that the passive alignment between the PD carrier120to which the SI-PD130is flip-chip bonded and the PLC chip110is sufficiently possible, if 0.2 dB tolerance is about +/−18 um.

FIG. 10is a flowchart illustrating a method of manufacturing a multi-channel receiver optical sub-assembly according to the present disclosure.

Referring toFIG. 10, according to this disclosure, first, the inclined surface112is formed on the other side of the PLC chip110(1001). The PLC chip110has on the top surface thereof the AWG or multi-channel straight optical waveguide, and the optical signal incident into one end is transmitted along the optical waveguide and then is outputted from the other side. In this disclosure, the inclined surface112is formed on the other side of the PLC chip110so that the other side of the PLC chip110has a preset inclination angle (specifically 45°) with respect to the bottom surface. The inclined surface112may be formed by the polishing or etching process.

According to this disclosure, the metal coated layer113is formed on the inclined surface112(1002). The metal coated layer113may be composed of Cr/Au, Cr/Ni/Au, Ti/Pt/Au or the like.

According to this disclosure, the SI-PD130having on the bottom surface thereof the lens is prepared (1003). Here, the lens131may be monolithic-integrated into the bottom surface of the SI-PD130using the photomask contact aligner. In various embodiments, the AR coating may be applied to the surface of the lens131.

Next, in this disclosure, the SI-PD130into which the lens131is integrated is bonded to the top surface of the PD carrier120(1004). Here, the SI-PD130and the PD carrier120are passively aligned using the plurality of alignment marks formed on the SI-PD130and the PD carrier120, and are bonded by flip-chip bonding.

Further, in this disclosure, the first SLC140for removing the power supply noise of the SI-PD130may be bonded to the top surface of the PD carrier120.

Subsequently, according to this disclosure, the PD carrier120to which the SI-PD130is bonded is bonded to the top surface of the PLC chip110(1005). Here, the PLC chip110and the PD carrier120are passively aligned using the plurality of alignment marks formed on the PLC chip110and the PD carrier120, and are bonded by epoxy.

Next, in this disclosure, the PLC chip110to which the PD carrier120is bonded is mounted on the first metal optical bench150(1006).

Thereafter, according to this disclosure, the second metal optical bench160is further mounted on the first metal optical bench150(1007). Here, the second metal optical bench160may be mounted on the first metal optical bench150to be adjacent to the PLC chip110, and the high resistance submount may be inserted between the first metal optical bench150and the second metal optical bench160.

Next, in this disclosure, the TIA array170, the RF-FPCB180, and the second SLC190for removing the power supply noise of the TIA array170are further mounted on the second metal optical bench160(1008). Here, the TIA array170and the RF-FPCB180may be mounted to be parallel with the SI-PD130.

In the multi-channel receiver optical sub-assembly according to this disclosure, the passive alignment makes it possible to implement the receiver optical sub-assembly in a very small size and at a low cost.

To be more specific, the multi-channel receiver optical sub-assembly according to this disclosure substitutes for the conventional receiver optical sub-assembly packaging structure that is complicated and expensive due to the active alignment between the SI-PD, the lens, and the PLC chip, thus being capable of reducing the manufacturing cost of the receiver optical sub-assembly.

Further, the multi-channel receiver optical sub-assembly according to this disclosure is configured such that the lens is formed on and monolithic-integrated into the SI-PD having a high refractive index, instead of the bulky glass lens used in the related art, thus allowing the receiver optical sub-assembly to be implemented in a small size.

Furthermore, the multi-channel receiver optical sub-assembly according to this disclosure is configured such that only the index matching transparent epoxy is applied to the section of the PLC chip polished at 45° and the upper and lower portions of the PD carrier made of the glass material without applying AR (Anti-Reflection) coating thereto, thus minimizing the effects of the optical reflection and reducing the cost of an AR coating process.

The multi-channel receiver optical sub-assembly according to this disclosure is configured such that the optical path is vertically arranged and the high frequency transmission line operated above 25 Gbps is horizontally arranged, thus minimizing impedance mismatch, suppressing a radiation loss occurring when the high frequency transmission line is vertically arranged, and preventing high frequency characteristics from being deteriorated, unlike the related art.