Prior art — US Patent 8805185

Here is an analysis of the prior art cited by US patent 8,805,185.

Analysis of Prior Art for US Patent 8,805,185

The following patents were cited as prior art during the examination of US patent 8,805,185. This analysis evaluates their relevance and potential to anticipate the claims of the '185 patent under 35 U.S.C. § 102.

1. US Patent 6,324,318 B1

Full Citation: US Patent 6,324,318 B1, "Redundant optical source switching method and wavelength division multiplexing transmission apparatus using the same"
Assignee: Fujitsu Limited
Filing Date: December 15, 1998
Publication Date: November 27, 2001
Brief Description: This patent describes a system for ensuring reliability in a WDM transmission system by using a redundant or backup light source. It includes a monitoring function that detects a failure in the primary light source (e.g., a drop in optical power). Upon detecting a failure, an optical switch is used to replace the failed primary signal with a signal from the redundant light source. The goal is to prevent signal loss and maintain the transmission.
Potential Anticipation: This reference is relevant as it discloses the concept of monitoring an optical signal and switching to a backup source upon failure. However, it appears to focus on switching to a redundant signal-carrying source rather than injecting a "dummy light" to stabilize an optical amplifier as claimed in the '185 patent. The '185 patent's novelty lies in using a non-signal dummy light specifically to maintain the total optical power for amplifier stability when a pass-through channel is interrupted. Therefore, US 6,324,318 B1 likely does not anticipate claim 1, as the purpose and nature of the replacement light source differ.

2. US Patent 6,449,070 B1

Full Citation: US Patent 6,449,070 B1, "Optical transmission device and wavelength-multiplexed optical transmission system"
Assignee: Fujitsu Limited
Filing Date: February 16, 1998
Publication Date: September 10, 2002
Brief Description: This patent details an optical transmission device, such as an optical add/drop multiplexer (OADM), that includes an optical amplifier. To maintain a constant output level from the amplifier, the system monitors the number of wavelength channels being transmitted. If a channel is dropped or lost, the system adjusts the gain of the optical amplifier to compensate for the change in total input power.
Potential Anticipation: This reference addresses the same problem as the '185 patent: stabilizing the output of an optical amplifier in a WDM system. It discloses monitoring the optical signal status. However, its solution is to control the amplification rate of the amplifier, not to introduce a dummy light source. The '185 patent specifically avoids adjusting the amplifier gain—which can introduce noise—by instead substituting the lost optical power with a dummy light. This fundamental difference in the control mechanism means US 6,449,070 B1 does not anticipate claim 1 of the '185 patent.

3. US Patent 6,714,740 B2

Full Citation: US Patent 6,714,740 B2, "Optical network and switch control method for use in the optical network"
Assignee: NEC Corporation
Filing Date: April 28, 1997
Publication Date: March 30, 2004
Brief Description: This patent describes a method for managing an optical network where light paths are established and released. It includes a supervisory system that monitors the status of optical signals. When a path is released or a failure is detected, the system can reroute signals or take other control actions to manage the network traffic and ensure integrity. The focus is on the network-level control and switching of signal paths.
Potential Anticipation: While this patent involves monitoring optical signals and responding to changes, its teachings are directed toward network-level path switching and control. It does not appear to disclose the specific problem of amplifier power stabilization at a node by injecting a dummy light signal when an incoming signal is interrupted. The solution described is centered on rerouting and resource management rather than maintaining a constant power level for an amplifier via a dummy source. Therefore, it is unlikely to anticipate the claims of the '185 patent.

4. US Patent Application Publication 2006/0018658 A1

Full Citation: US 2006/0018658 A1, "Wavelength division multiplexing optical transmission system"
Inventor: Shota Mori
Filing Date: July 20, 2004
Publication Date: January 26, 2006
Brief Description: This application describes a WDM transmission system that aims to stabilize the output of an optical amplifier. It discloses a mechanism that monitors the input optical signal. If the number of channels decreases, the system introduces a compensating light (dummy light) into the optical amplifier to keep the total input power constant. This prevents fluctuations in the amplifier's output gain.
Potential Anticipation: This reference is highly relevant as it discloses the core concept of monitoring an input signal and injecting a compensating or "dummy" light to stabilize an optical amplifier. It teaches a monitoring unit, a source for compensating light, and multiplexing it into the signal path. This appears to describe the key elements of claim 1 of the '185 patent. A detailed analysis would be required to determine if all limitations of claim 1 are explicitly or inherently disclosed. Specifically, the context of a "pass-through" signal in a device with both a receiver and transmitter, as claimed in the '185 patent, would need to be compared. However, on its face, US 2006/0018658 A1 presents a strong case for potentially anticipating at least claim 1 of US 8,805,185.