Patent Description:
Computing platforms are increasingly using photonic systems that use silicon as an optical medium. Today, these photonic systems, which may be implemented as a PIC, transmit and receive optical signals via separate integrated circuit units.

<CIT> and <CIT> disclose photonic transceiver apparatuses comprising isolators. <CIT> and <CIT> discloses optical modules comprising isolators.

The present invention concerns a photonic transceiver apparatus according to claim <NUM> and a method for creating a photonic transceiver apparatus according to claim <NUM>. Embodiments described herein are directed to an optical transceiver IC having both the transmitter and receiver integrated on the same photonic integrated circuit (PIC). An optical transceiver IC may include a transmit optical subassembly (TOSA) that converts electrical signals into an optical signal, and a receiver optical subassembly (ROSA) that converts optical signals to an electrical signal. In embodiments described herein, the TOSA and ROSA are combined into a single unit that incorporates an optical isolator, thus eliminating the need for an external isolator unit. In embodiments, transmitter optical pathways (or transmitter channel) and receiver optical pathways (receiver channel) on the optical transceiver IC may share a single lens array, and incorporate a compensator block to equalize the transmitter and receiver optical pathways in the transceiver. These embodiments may reduce component and assembly costs, as well the overall footprint and energy requirements for implementing a TOSA and ROSA.

Legacy implementations require separate devices for TOSA and ROSA. In legacy implementations, the TOSA channels, or optical transmitter pathways, require an optical isolator to minimize the feedback to the laser source in order to maintain lazing stability. Typically, ROSA channels, or optical receiver pathways, do not require an optical isolator. In legacy implementations, the transmitter design is generally more challenging as it requires mode matching between the laser source/waveguide and an outgoing single mode fiber. These requirements may be somewhat relaxed for short range transmission multimode fibers. The receiver solutions are generally simpler and are based on coupling the light from a waveguide or a fiber to a photodiode, or an array of photodiodes.

These legacy implementations may require active alignment of the fiber block. The fiber block may be subject to stress imposed by fibers or shifts caused by epoxy curing or thermal expansion coefficient mismatch. This may affect coupling efficiency, reducing yield and increasing failure rate of components. In addition, these legacy designs require different optical design for optical transmitter pathways and optical receiver pathways, which may also be referred to as optical branches. This in turn necessitates manufacturing of two separate PICs and actively aligning both units. This significantly increases the cost and the footprint of the final implementation. Legacy waveguide butt-coupling solutions can be combined into a single unit, however there is a separate external optical isolator required for each transmit channel, for example an in-line optical isolator. This approach may be cost prohibitive in high-volume. In addition, legacy butt-coupled solutions typically only work with low numerical aperture (NA) waveguides that have reasonably large alignment tolerances so that a lens for mode-matching may be eliminated.

In the following description, various aspects of the illustrative implementations will be described using terms commonly employed by those skilled in the art to convey the substance of their work to others skilled in the art. However, it will be apparent to those skilled in the art that embodiments of the present disclosure may be practiced with only some of the described aspects. For purposes of explanation, specific numbers, materials, and configurations are set forth in order to provide a thorough understanding of the illustrative implementations. It will be apparent to one skilled in the art that embodiments of the present disclosure may be practiced without the specific details. In other instances, well-known features are omitted or simplified in order not to obscure the illustrative implementations.

In the following detailed description, reference is made to the accompanying drawings that form a part hereof, wherein like numerals designate like parts throughout, and in which is shown by way of illustration embodiments in which the subject matter of the present disclosure may be practiced. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of embodiments is defined by the appended claims and their equivalents.

For the purposes of the present disclosure, the phrase "A, B, and/or C" means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C).

The description may use perspective-based descriptions such as top/bottom, in/out, over/under, and the like. Such descriptions are merely used to facilitate the discussion and are not intended to restrict the application of embodiments described herein to any particular orientation.

The term "coupled with," along with its derivatives, may be used herein. "Coupled" may mean one or more of the following. "Coupled" may mean that two or more elements are in direct physical or electrical contact. However, "coupled" may also mean that two or more elements indirectly contact each other, but yet still cooperate or interact with each other, and may mean that one or more other elements are coupled or connected between the elements that are said to be coupled with each other. The term "directly coupled" may mean that two or more elements are in direct contact.

<FIG> is a top-down view of an optical transceiver IC that includes a lens array and a fiber block to which an optical isolator and a compensator block are attached, in accordance with the present invention. Transceiver IC <NUM> includes a lens array <NUM> and a fiber block <NUM>. The transceiver IC <NUM> allows the transmission of a transmitter optical signal <NUM> from the lens array <NUM> through a waveguide <NUM> of fiber block <NUM>, as well as the reception of a receiver optical signal <NUM> from the waveguide <NUM> of fiber block <NUM> by the optical array <NUM>.

The transmission of the transmitter optical signal <NUM> will pass through a focus lens <NUM>, and will pass through an optical isolator <NUM> as the signal enters fiber <NUM> of fiber block <NUM>. The optical isolator <NUM> is coupled, optically and/or physically, with the fiber block <NUM> and intersects transmitter optical signal <NUM>. In embodiments, the optical isolator <NUM> is an optical component that allows transmission of light in one direction, and may be used to prevent unwanted optical feedback. In embodiments, the optical isolator <NUM> may be a Faraday rotator that includes an input polarizer 108a, which may also be referred to as a <NUM>° polarizer, a Faraday rotator 108b, and an analyzer 108c, which may also be referred to as a <NUM>° polarizer. The <NUM>° polarizer 108a is aligned with innate polarization of the laser source, typically a transverse electric (TE) mode, and passes the incoming light with little attenuation. The Faraday rotator 108b rotates the incoming light polarization by <NUM>°, so it freely passes the <NUM>° polarizer 108c. The optical isolator <NUM> blocks light of any polarization coming from the side of the <NUM>° polarizer 108c by first polarizing it at <NUM>° and then rotating the light polarization by additional <NUM>° to the total of <NUM>° so it is cut by the <NUM>° polarizer 108a.

The reception of the receiver optical signal <NUM> will pass through a compensator block <NUM> on its way to focus lens <NUM> of the lens array <NUM>. In embodiments, the compensator block <NUM> includes a thickness of glass material, or of other transparent materials discussed below. The compensator block <NUM> is to equalize the transmitter optical signal <NUM> in the receiver optical signal <NUM> between the lens array <NUM> and the fiber block <NUM>. Without the compensator block <NUM>, the transmitter optical signal <NUM> and the receiver optical signal <NUM> would focus at different locations. This equalization allows the transmission and reception functions to be merged into one common focusing lens array <NUM> and fiber block <NUM>. In embodiments, the dimensions of the optical isolator <NUM> and the compensator block <NUM> may be adjusted depending upon the distance and/or positions of the focusing lens array <NUM> and the fiber block <NUM>.

In embodiments, both optical isolator <NUM> and compensator block <NUM> are of similar total thickness. To achieve this, in embodiments, the index of refraction of the compensator block <NUM> should be between the indices of refraction of the polarizer layers 108a, 108c, for example approximately <NUM>, and that of the Faraday rotator 108b. In embodiments, the Faraday rotator 108b may be made of Yttrium Iron Garnet, with an index of refraction of approximately <NUM>. In embodiments, heavy Flint glasses such as SF-<NUM>, which may have an example index of refraction of <NUM>, or Lanthanum Crown glasses may be used for the compensator block <NUM>. Other materials may include other high index glasses or crystalline materials such as Sapphire or Silicon Nitride.

<FIG> is a top-down view of an optical transceiver IC that includes a lens array and a fiber block that supports multiple transmit and receive optical pathways to which an optical isolator and a compensator block are attached, in accordance with various embodiments. Transceiver IC <NUM> shows a lens array <NUM> and a fiber block <NUM>, which may be similar to lens array <NUM> and fiber block <NUM> of <FIG>. Transceiver IC <NUM> has a number of transmit channels <NUM> that may include a number of transmitter optical signals <NUM>. Transceiver IC <NUM> may also include a number of receive channels <NUM> that may include a number of receiver optical signals <NUM>. Both transmission and reception use the same lens array <NUM> and fiber block <NUM>.

As shown, each of the transmitter optical signals <NUM>, which may be similar to transmitter optical signals <NUM> of <FIG>, of the transmit channels <NUM> pass through a lens <NUM>, which may be similar to lens <NUM> of <FIG> and into a common optical isolator <NUM>, which may be similar to optical isolator <NUM> of <FIG>. The transmitter optical signals <NUM> then focus into the fibers <NUM> of the transmit channels <NUM>. In embodiments, the optical isolator <NUM> may be broken up into individual optical isolators (not shown) for use by one or more subsets of the transmitter optical signals <NUM>.

Each of the receiver optical signals <NUM>, which may be similar to receiver optical signals <NUM> of <FIG>, of the receive channels <NUM> pass from a waveguide <NUM>, which may be similar to waveguide <NUM> of <FIG>, through a common compensator block <NUM>, which may be similar to compensator block <NUM> of <FIG>. The receiver optical signals <NUM> then pass through a receiver lens <NUM> of the receiver channels <NUM> of the focusing lens array <NUM>. In embodiments, the compensator block <NUM> may be broken into individual compensator blocks (not shown) for use -.

It should be appreciated that although the lenses <NUM>, <NUM> of the lens array <NUM> are shown in a line, in other embodiments the lenses <NUM>, <NUM> may appear as a two-dimensional array on the lens array <NUM>. Similarly, the corresponding waveguides <NUM>, <NUM> may appear as a two dimensional array on the fiber block <NUM>.

<FIG> shows top, side, and perspective views of optical isolators and compensator blocks interacting with optical pathways, in accordance with various embodiments. <FIG> shows various examples related to optical transceiver IC <NUM> of <FIG>. Diagram <NUM> shows a side view of optical transceiver IC <NUM>, with lens array <NUM>, optical isolator <NUM>, compensator block <NUM> (positioned behind and partially obscured by optical isolator <NUM>), fiber block <NUM>, and waveguide <NUM>, which may be similar to lens array <NUM>, optical isolator <NUM>, compensator block <NUM>, fiber block <NUM>, and waveguide <NUM> of <FIG>.

As shown, a face <NUM> of the fiber block <NUM> is angled and is not perpendicular with respect to the waveguide <NUM> within the fiber block <NUM>. In embodiments, the face <NUM> is polished at an angle to mitigate back reflection. In other embodiments, a similar angle affect may be achieved using an angled slab of any transparent material (not shown) coupled with a perpendicular face (not shown) of the fiber block <NUM> to cause the angle of the optical isolator <NUM> and the compensator block <NUM>. However, an angled slab of transparent material (not shown) may cause a shift of a chief ray of the transmitter optical signal <NUM>, and its resulting focus. In embodiments, the thickness of the compensator block <NUM> should be such that the chief rays, e.g. the chief rays of the transmitter optical path <NUM> and the receiver optical path <NUM> of <FIG>, would focus at a same height and at a same distance from their respective focus lenses, for example lens <NUM> and lens <NUM> of <FIG>. In embodiments, the angle of the face <NUM> off of the perpendicular of the waveguide <NUM> may be adjusted to produce better results.

In embodiments, thickness variations of the isolator <NUM> and/or compensator block <NUM> may cause vertical displacement of the focal spots, and coupling loss in one of the transmitter or receiver optical signal <NUM>. In these embodiments, a small-angled role correction of a lens, for example in lens <NUM>, <NUM> of <FIG>, or a small-angled role correction of the fiber block <NUM> may be used to compensate for these variations.

Diagram <NUM> shows a side view of diagram <NUM>, in a wireframe form without the fiber block <NUM>. Diagram <NUM> shows a perspective view of diagram <NUM> in a wireframe form without the fiber block <NUM>. Diagram <NUM> show a top-down view of diagram <NUM> in a wireframe form without the fiber block <NUM>. In embodiments, the fiber polish angle may differ for the Tx and Rx paths. For cost reduction, the fiber polish angle can be the same for both paths. In embodiments, the fiber block is polished first, then the optical isolator and the compensator are cemented to it. In embodiments, an additional lens surface in <NUM> at opposite side of <NUM> and <NUM> of <FIG> for either Tx or Rx may be used to achieve the effect of optical path "equalization.

<FIG> is a top-down view of an optical transceiver IC that includes two lens arrays and a fiber block, with an optical isolator and compensator block between the two lens arrays, in accordance with various embodiments. Transceiver IC <NUM> includes a first lens array <NUM>, which may be similar to lens array <NUM> of <FIG>, with transmit channels <NUM> and receive channels <NUM>, which may be similar to the transmit channels <NUM> and transmit channels <NUM> of <FIG>. Transmit channels <NUM> include transmitter optical signals <NUM>, which may be similar to transmitter optical signals <NUM> of <FIG>. Receive channels <NUM> include receiver optical signals <NUM>, which may be similar to receiver optical signals <NUM> of <FIG> Transceiver IC <NUM> also includes the fiber block <NUM>, which may be similar to fiber block <NUM> of <FIG>, that is optically coupled with a second lens array <NUM>, the may be similar to lens array <NUM> of <FIG>.

Transceiver IC <NUM> also includes a dual-stage isolator <NUM> that is positioned between the first lens array <NUM> and the second lens array <NUM> that intercepts the transmit optical paths <NUM> as they travel from lens <NUM> to lens <NUM> and into fiber <NUM>, which may be similar to waveguide <NUM> of <FIG>. In embodiments, the dual-stage isolator <NUM> may be a single-stage isolator, or another optical isolator with a different design.

Transceiver IC <NUM> also includes a compensator block <NUM> that is positioned between the first lens array <NUM> and the second lens array <NUM> that intercepts the receiver optical signal <NUM> from receive waveguide <NUM> of fiber block <NUM> through focus lens <NUM> of the second optical array <NUM> to the focus lens <NUM> of the first optical array <NUM>. In embodiments, the compensator block <NUM> may be made of one or more layers of transparent material as described above.

In embodiments, the dual-stage isolator <NUM> or the compensator block <NUM> may not be physically coupled to the first lens array <NUM>, the second lens array <NUM>, or the fiber block <NUM>. In embodiments, the dual-stage isolator <NUM> or the compensator block <NUM> may not be positioned parallel to the first optical array <NUM> or the second optical array <NUM>, and may be tilted in either a horizontal plane (as shown) or vertical plane. In embodiments, the dual-stage isolator <NUM> and the compensator block <NUM> may be oriented in different directions. In other embodiments, the dual-stage isolator <NUM> and the compensator block <NUM> may be surrounded by air, and/or may be physically coupled with a substrate to maintain their orientation within the transceiver IC <NUM>.

In other embodiments of a multi-channel implementation there may be a different number of transmit channels <NUM> and receive channels <NUM>. In other embodiments, the positioning of the transmit channels <NUM> and the receive channels <NUM> may be unequally spaced, or may be staggered throughout the first optical array <NUM>. In some embodiments, some transmit channels <NUM> may not require isolation, and may pass through the compensator block <NUM>. In embodiments, the lenses <NUM>, <NUM>, <NUM>, <NUM> may be single-lens designs, or dual-lens designs, or a combination of both. In embodiments, dual-lens design may allow light traveling in the path of the transmitter optical signal <NUM> and the path of the receiver optical signal <NUM> to be brought near to collimation by the first set of lenses, passing through the compensator block <NUM> or optical isolator <NUM> and then focused back, for example, on the fiber block <NUM>. In embodiments, the transceiver IC <NUM> may be coupled with an optical module that has an electrical interface and an optical interface.

<FIG> is a process for creating a portion of an optical transceiver IC with an isolator and compensator unit, in accordance with various embodiments. Process <NUM> may be implemented using the various techniques and apparatuses described herein, in particular with respect to <FIG>.

At block <NUM>, the process includes providing a fiber block on an integrated circuit that includes a first optical path for optical transmission and a second optical path for optical reception. The fiber block may include fiber block <NUM> of <FIG>, fiber block <NUM> of <FIG>, fiber block <NUM> of <FIG>, or fiber block <NUM> of <FIG>. The first optical path for transmission may include optical path <NUM> of <FIG>, optical path <NUM> of <FIG>, and/or optical path <NUM> of <FIG>. The second optical path for optical reception may include optical path <NUM> of <FIG>, optical path <NUM> of <FIG>, and/or optical path <NUM> of <FIG>.

At block <NUM>, the process may include providing a lens array to the same integrated circuit, and optically coupling the lens array with the fiber block. The lens array and fiber block may include lens array <NUM> and fiber block <NUM> of <FIG>, lens array <NUM> and fiber block <NUM> of <FIG>, lens array <NUM> and fiber block <NUM> of <FIG>, and first lens array <NUM> and/or second lens array <NUM> and fiber block <NUM> of <FIG>.

At block <NUM>, the process may include aligning a first focus lens of the lens array with the first optical path. In embodiments, this may represent a transmission channel. The first focus lens and the first optical path may include lens <NUM> and optical path <NUM> of <FIG>, lens <NUM> and optical path <NUM> of <FIG>, or lens <NUM> and optical path <NUM> of <FIG>.

At block <NUM>, the process may include aligning a second focus lens of the lens array with the second optical path. In embodiments, this may represent a receive channel. The second focus lens and the second optical path may include lens <NUM> and optical path <NUM> of <FIG>, lens <NUM> and optical path <NUM> of <FIG>, and/or lens <NUM> and optical path <NUM> of <FIG>.

At block <NUM>, the process may include providing an optical isolator block to the same integrated circuit, and coupling the optical isolator block with the fiber block in the first optical path. In embodiments, the optical isolator block and the fiber block may include isolator block <NUM> and fiber block <NUM> of <FIG>, optical isolator block <NUM> and fiber block <NUM> of <FIG>, or dual-isolator block <NUM> and fiber block <NUM> of <FIG>.

At block <NUM>, the process may include providing a compensator block to the same integrated circuit, and coupling the compensator block with the fiber block in the second optical path, the compensator block equalizing the optical path of the first optical path and the second optical path. In embodiments, the compensator block and the fiber block may include compensator block <NUM> and fiber block <NUM> of <FIG>, compensator block <NUM> and fiber block <NUM> of <FIG>, or compensator block <NUM> and fiber block <NUM> of <FIG>.

It should be appreciated that any of the blocks above representing stages in the process <NUM> may be performed in any order, with one or more blocks being omitted or with one or more blocks being repeated.

Embodiments of the present disclosure may be implemented into a system using any suitable hardware and/or software to configure as desired. <FIG> schematically illustrates a computing device <NUM> in accordance with one embodiment. The computer system <NUM> (also referred to as the electronic system <NUM>) as depicted can embody an optical transceiver IC with an isolator and compensator unit, according to any of the several disclosed embodiments and their equivalents as set forth in this disclosure. In particular, one or more of the communication circuits <NUM>, <NUM> may embody an optical transceiver IC with an isolator and compensator unit. The computer system <NUM> may be a mobile device such as a netbook computer. The computer system <NUM> may be a mobile device such as a wireless smart phone. The computer system <NUM> may be a desktop computer. The computer system <NUM> may be a hand-held reader. The computer system <NUM> may be a server system. The computer system <NUM> may be a supercomputer or high-performance computing system.

In an embodiment, the electronic system <NUM> is a computer system that includes a system bus <NUM> to electrically couple the various components of the electronic system <NUM>. The system bus <NUM> is a single bus or any combination of busses according to various embodiments. The electronic system <NUM> includes a voltage source <NUM> that provides power to the integrated circuit <NUM>. In some embodiments, the voltage source <NUM> supplies current to the integrated circuit <NUM> through the system bus <NUM>.

The integrated circuit <NUM> is electrically coupled to the system bus <NUM> and includes any circuit, or combination of circuits according to an embodiment. In an embodiment, the integrated circuit <NUM> includes a processor <NUM> that can be of any type. As used herein, the processor <NUM> may mean any type of circuit such as, but not limited to, a microprocessor, a microcontroller, a graphics processor, a digital signal processor, or another processor. In an embodiment, the processor <NUM> includes, or is coupled with, an optical transceiver IC with an isolator and compensator unit, as disclosed herein. In an embodiment, SRAM embodiments are found in memory caches of the processor. Other types of circuits that can be included in the integrated circuit <NUM> are a custom circuit or an application-specific integrated circuit (ASIC), such as a communications circuit <NUM> for use in wireless devices such as cellular telephones, smart phones, pagers, portable computers, two-way radios, and similar electronic systems, or a communications circuit for servers. In an embodiment, the integrated circuit <NUM> includes on-die memory <NUM> such as static random-access memory (SRAM). In an embodiment, the integrated circuit <NUM> includes embedded on-die memory <NUM> such as embedded dynamic random-access memory (eDRAM).

In an embodiment, the integrated circuit <NUM> is complemented with a subsequent integrated circuit <NUM>. Useful embodiments include a dual processor <NUM> and a dual communications circuit <NUM> and dual on-die memory <NUM> such as SRAM. In an embodiment, the dual integrated circuit <NUM> includes embedded on-die memory <NUM> such as eDRAM.

In an embodiment, the electronic system <NUM> also includes an external memory <NUM> that in turn may include one or more memory elements suitable to the particular application, such as a main memory <NUM> in the form of RAM, one or more hard drives <NUM>, and/or one or more drives that handle removable media <NUM>, such as diskettes, compact disks (CDs), digital variable disks (DVDs), flash memory drives, and other removable media known in the art. The external memory <NUM> may also be embedded memory <NUM> such as the first die in a die stack, according to an embodiment.

In an embodiment, the electronic system <NUM> also includes a display device <NUM>, an audio output <NUM>. In an embodiment, the electronic system <NUM> includes an input device such as a controller <NUM> that may be a keyboard, mouse, trackball, game controller, microphone, voicerecognition device, or any other input device that inputs information into the electronic system <NUM>. In an embodiment, an input device <NUM> is a camera. In an embodiment, an input device <NUM> is a digital sound recorder. In an embodiment, an input device <NUM> is a camera and a digital sound recorder.

As shown herein, the integrated circuit <NUM> can be implemented in a number of different embodiments, including a package having an optical transceiver IC with an isolator and compensator unit, according to any of the several disclosed embodiments and their equivalents, an electronic system, a computer system, one or more methods of fabricating an integrated circuit, and one or more methods of fabricating an electronic assembly that includes an optical transceiver with an isolator and compensator unit, according to any of the several disclosed embodiments as set forth herein in the various embodiments and their art-recognized equivalents. The elements, materials, geometries, dimensions, and sequence of operations can all be varied to suit particular I/O coupling requirements including array contact count, array contact configuration for a microelectronic die embedded in a processor mounting substrate according to any of the several disclosed optical transceivers with an isolator and compensator unit and their equivalents. A foundation multi-layer PCB may be included, as represented by the dashed line of <FIG>. Passive devices may also be included, as is also depicted in <FIG>.

Various embodiments may include any suitable combination of the above-described embodiments including alternative (or) embodiments of embodiments that are described in conjunctive form (and) above (e.g., the "and" may be "and/or"). Furthermore, some embodiments may include one or more articles of manufacture (e.g., non-transitory computerreadable media) having instructions, stored thereon, that when executed result in actions of any of the above-described embodiments. Moreover, some embodiments may include apparatuses or systems having any suitable means for carrying out the various operations of the above-described embodiments.

The above description of illustrated implementations, including what is described in the Abstract, is not intended to be exhaustive or to limit the embodiments of the present disclosure to the precise forms disclosed. While specific implementations and examples are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the present invention, as defined by the attached claims.

Claim 1:
A photonic transceiver apparatus (<NUM>; <NUM>; <NUM>) comprising:
a fiber block (<NUM>; <NUM>; <NUM>; <NUM>, <NUM>) disposed on an integrated circuit that includes a first optical path for optical transmission and a second optical path for optical reception;
a lens array (<NUM>; <NUM>; <NUM>; <NUM>) disposed on the same integrated circuit, and optically coupled with the fiber block (<NUM>; <NUM>; <NUM>; <NUM>, <NUM>), the lens array (<NUM>; <NUM>; <NUM>; <NUM>) including a first focus lens (<NUM>; <NUM>; <NUM>, <NUM>) and a second focus lens (<NUM>; <NUM>; <NUM>, <NUM>) aligned, respectively, with the first optical path and the second optical path;
an optical isolator block (<NUM>; <NUM>; <NUM>; <NUM>) coupled with the fiber block (<NUM>; <NUM>; <NUM>; <NUM>, <NUM>) and disposed between the fiber block (<NUM>; <NUM>; <NUM>; <NUM>, <NUM>) and the lens array (<NUM>; <NUM>; <NUM>; <NUM>) in the first optical path on the same integrated circuit, wherein the optical isolator block (<NUM>; <NUM>; <NUM>; <NUM>) is to reduce the feedback to a laser source during optical transmission; and
a compensator block (<NUM>; <NUM>; <NUM>; <NUM>) coupled with the fiber block (<NUM>; <NUM>; <NUM>; <NUM>, <NUM>) and disposed between the fiber block (<NUM>; <NUM>; <NUM>; <NUM>, <NUM>) and the lens array (<NUM>; <NUM>; <NUM>; <NUM>) in the second optical path on the same integrated circuit, wherein the compensator block (<NUM>; <NUM>; <NUM>; <NUM>) is to equalize the optical path of the first optical path and the second optical path.