Obviousness

Here is an analysis of the obviousness of US patent 8,805,185 under 35 U.S.C. § 103, based on the provided prior art.

Obviousness Analysis of US Patent 8,805,185

A determination of obviousness under 35 U.S.C. § 103 requires analyzing whether the differences between the claimed invention and the prior art are such that the subject matter as a whole would have been obvious at the time the invention was made to a person having ordinary skill in the art (PHOSITA).

Based on the provided prior art, the claims of US patent 8,805,185 appear to be obvious over the combination of US Patent Application Publication 2006/0018658 A1 (hereinafter "Mori") and US Patent 6,449,070 B1 (hereinafter "Fujitsu '070").

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1. Scope and Content of the Prior Art

• Mori (US 2006/0018658 A1): Mori discloses the core inventive concept of the '185 patent. It explicitly teaches a solution to the problem of stabilizing the output of an optical amplifier in a WDM system when the number of input channels decreases. The proposed solution is to:

  • Monitor the input optical signal.
  • Detect a decrease in the number of channels (i.e., an "input interruption").
  • Inject a "compensating light" (equivalent to the '185 patent's "dummy light") into the optical amplifier to keep the total input power constant.
  • Use a controller to manage the emission of this compensating light based on the monitored signal.

  Mori therefore teaches the essential elements of claim 1 related to the fail-safe mechanism: a dummy light source, a monitoring unit, a controller to activate the source upon signal interruption, and a multiplexer to combine the dummy light with other signals before amplification.

• Fujitsu '070 (US 6,449,070 B1): Fujitsu '070 describes the structural and functional context in which the invention of the '185 patent operates. It details an optical transmission device, specifically an optical add/drop multiplexer (OADM), which is a standard component in WDM networks. This device inherently includes:

  • A receiver and a transmitter structure.
  • The ability to demultiplex an incoming WDM signal.
  • The function of "dropping" (demodulating) specific wavelengths for local reception.
  • The function of allowing other wavelengths to "pass-through" to the next node.
  • The function of "adding" new, locally generated signals to the pass-through signals for onward transmission.

  Crucially, Fujitsu '070 also recognizes the exact problem addressed by Mori and the '185 patent: that the output level of the device's optical amplifier becomes unstable when a channel is dropped or lost. The solution in Fujitsu '070, however, is to adjust the gain of the amplifier rather than adding a dummy light.

2. Differences Between the Prior Art and the Claims

Mori teaches the specific power stabilization method (injecting dummy light) but does not explicitly describe implementing it within a device having the full add/drop/pass-through architecture as laid out in the preamble of claim 1.

Fujitsu '070 teaches the exact add/drop/pass-through architecture and identifies the same power stabilization problem, but it applies a different, known solution (adjusting amplifier gain).

The primary difference between the claimed invention and the combined teachings of the prior art is the specific application of Mori's dummy light solution within the OADM architecture of Fujitsu '070.

3. Motivation to Combine

A person having ordinary skill in the art would have been motivated to combine the teachings of Mori and Fujitsu '070 for the following reasons:

1. Identical Problem: Both Fujitsu '070 and Mori address the identical, well-known problem of maintaining stable output power from an optical amplifier in a WDM system when the number of wavelength channels fluctuates. A PHOSITA, starting with the OADM device in Fujitsu '070, would be confronted with this exact problem.

2. Known Disadvantages of the Fujitsu '070 Solution: The '185 patent itself notes in its "Background Art" section that simply increasing the amplification rate of an optical amplifier can amplify noise components along with the signal. A PHOSITA would have been aware of this trade-off and would have been motivated to seek alternative solutions that did not have this disadvantage.

3. Mori as a Direct, Alternative Solution: In seeking a better solution to the problem identified in Fujitsu '070, a PHOSITA would have readily found Mori. Mori presents a direct, elegant, and alternative solution to the very same problem. It proposes maintaining constant input power rather than adjusting the amplifier's gain, thus avoiding the issue of noise amplification.

4. Predictable Result: Applying the power stabilization technique from Mori to the OADM device from Fujitsu '070 would be a matter of simple substitution. A PHOSITA would replace Fujitsu '070's gain-control mechanism with Mori's dummy-light injection mechanism. This combination would be straightforward, involving known optical components (light sources, controllers, multiplexers) to achieve the predictable result of a stabilized amplifier output without increased noise. This is not the product of inventive insight but rather the application of one known solution to a known problem in a known context.

Conclusion

The independent claim of US patent 8,805,185 would have been obvious to a person of ordinary skill in the art. The claim simply applies the known power-stabilization technique taught by Mori (using a controlled dummy light source) to the conventional WDM add/drop multiplexer architecture taught by Fujitsu '070. A PHOSITA would have been motivated to make this combination to solve the known problem of amplifier instability in a way that avoids the noise-amplification drawbacks of the gain-control method also taught in the prior art.