Obviousness

Obviousness Analysis of US10714890 under 35 U.S.C. § 103

This analysis identifies combinations of prior art references that would render the claims of US Patent 10714890 obvious to a person having ordinary skill in the art (POSA). A POSA in this field would typically possess a degree in electrical engineering, optical engineering, or a related discipline, coupled with practical experience in designing and manufacturing optical transceivers, laser diodes, and photodiodes, and would be familiar with the challenges of miniaturization and RF signal integrity in such devices.

The independent claims of US10714890 (Claims 1, 11, and 15) primarily focus on a Transmitter Optical Subassembly (TOSA) module where monitor photodiodes (MPDs) are mounted vertically on a feedthrough device, substantially transverse to a laser diode (LD) mounting surface. This arrangement allows the MPD to capture back-side emission from the LD, while simultaneously reducing the overall TOSA housing dimensions and enabling shorter, more direct radio frequency (RF) traces to the LD, thereby improving RF signal quality.

Prior Art References:

1. US20040163836A1 (Kumar Dev E) – "Multi-layer ceramic feedthrough structure in a transmitter optical subassembly": This reference discloses a multi-layer ceramic feedthrough structure designed for a TOSA, providing electrical interconnections between internal and external components. It highlights the use of a feedthrough as a structural and electrical interface within the TOSA.
2. US20180138657A1 (Furukawa Electric Co., Ltd.) – "Semiconductor laser module": This patent describes a semiconductor laser module including an LD and an MPD. The MPD is mounted on a submount and specifically arranged to receive backward light (back-side emission) from the rear end face of the laser diode for monitoring purposes.

Combination: US20180138657A1 (Furukawa) in view of US20040163836A1 (Kumar)

Reasoning for Obviousness:

The background section of US10714890 explicitly identifies two significant challenges with existing TOSA designs, particularly those with MPDs positioned behind or adjacent to the LD (an arrangement exemplified by Furukawa):

1. Increased Housing Length: This traditional MPD placement necessitates larger TOSA housings, leading to an "overall increase in housing length along dimension D."
2. Degraded RF Performance: The positioning of the MPD behind the LD requires lengthening interconnect circuitry, such as wire bonds, from the laser diode driver (LDD) to the LD. These extended wire bonds "can result in time-of-flight (TOF) delays and impedance matching issues as well as worse RF performance."

A person having ordinary skill in the art (POSA) would be well aware of these problems and highly motivated to address them, especially given the continuous industry drive for miniaturization and enhanced high-speed data transmission quality in optical transceivers.

• Motivation to Combine Furukawa and Kumar:

  • Miniaturization: Furukawa teaches the effective use of back-side emission for optical power monitoring, a desirable feature for closed-loop control of laser output. However, its typical planar mounting of the MPD behind the LD, as depicted in Furukawa's FIG. 1 and also criticized in US10714890's FIG. 10, directly contributes to the undesired increase in TOSA length. To reduce this length, a POSA would logically seek to rearrange components to occupy less linear space.
  • Improved RF Signal Integrity: The issue of long wire bonds causing RF signal degradation is a known problem that directly impacts the performance of high-speed optical transceivers. Freeing up space for shorter, more direct RF traces to the LD would be a clear objective for a POSA.

• Applying the Combination to the Claims:

  • Vertical MPD Mounting on Feedthrough: Kumar teaches the use of a feedthrough device as a multi-layer ceramic structure that provides electrical interconnections and potentially houses components within a TOSA. By its nature, a feedthrough can offer various surfaces and extend in multiple dimensions within the TOSA cavity. A POSA, faced with the problems of TOSA length and RF performance degradation, would find it an obvious design modification to utilize a surface of the existing feedthrough (Kumar) to mount the MPD (Furukawa). Specifically, mounting the MPD on a vertical surface of the feedthrough, positioned substantially transverse to the LD mounting surface, directly solves the problem of increased TOSA length by moving the MPD out of the linear path behind the LD.
  • Optical Alignment via Back-Side Emission: Furukawa explicitly teaches that the MPD is "arranged on an optical path of backward light... emitted from a rear end face of the laser diode." A POSA would understand how to maintain this optical alignment even when relocating the MPD to a vertical surface on the feedthrough. The feedthrough's role in electrical interconnection (Kumar) would naturally extend to routing the MPD's electrical signals.
  • RF Trace Routing: With the MPD moved to a vertical position, the space previously occupied by the MPD behind the LD becomes available. A POSA would immediately recognize that this freed-up space could be used to pattern shorter, more direct RF conductive traces on the feedthrough device's surfaces, extending closer to the LD. This enables shorter wire bonds, thereby mitigating the TOF delays and impedance mismatching issues highlighted in the background of US10714890. The concept of patterning conductive traces on a feedthrough is implicitly taught by Kumar's disclosure of electrical interconnections.

• Claim Elements Addressed:

  • Claim 1 (TOSA Module): The LD mounting surface and LD with back-side emission are taught by Furukawa. The base portion comprising a feedthrough device is taught by Kumar. Providing a "vertical MPD mounting surface" on the feedthrough and disposing an MPD thereon, optically aligned with the LD's back-side emission via a transverse arrangement, would be an obvious design choice for a POSA motivated to overcome the size and RF performance limitations of the prior art.
  • Claim 11 (Method): The method steps of mounting an MPD to a vertical mounting surface of a feedthrough, patterning conductive traces on the feedthrough, and inserting the feedthrough into the housing to achieve optical coupling with the back-side emission of LDs, represent a logical sequence of manufacturing steps for implementing the combined design. Integrating electrical traces with a feedthrough is known from Kumar, and aligning optical components is standard practice.
  • Claim 15 (Multi-Channel Optical Transceiver Module): This claim incorporates the TOSA module of Claim 1 into a broader transceiver system. If the TOSA module itself is obvious, its integration into a standard multi-channel optical transceiver with a PCBA and a multi-channel receiver optical subassembly (ROSA) would also be considered obvious.

Conclusion:

A person having ordinary skill in the art, motivated by the well-known challenges of miniaturization and improving RF signal integrity in TOSA designs (as articulated in the background of US10714890), would have found it obvious to combine the teachings of US20180138657A1 (Furukawa), which discloses using back-side emission for MPD monitoring, with US20040163836A1 (Kumar), which discloses the use of a feedthrough device for electrical and structural integration within a TOSA. The specific design choice to mount the MPD on a vertical surface of the feedthrough, transverse to the LD, directly addresses and overcomes the known problems of increased TOSA length and degraded RF performance due to long wire bonds, which were prevalent in prior art designs like that shown in Furukawa. This combination of known elements to achieve predictable results in a field driven by continuous improvement in size and performance would be considered obvious under 35 U.S.C. § 103.