Patent ID: 9331844
Filing Date: 2016-05-03
CPC Classification: H04J,H04L

Claim Text:
1. A method of distributing reference frequency and timing information in a network with pairs of first and second optical fibers in optical fiber connections between network nodes, for transmission of optical data signals separately in mutually opposite directions between the network nodes respectively, the method comprising: generating a first timing signal in a first node of the network; optically combining the first timing signal with an optical data signal so as to form a combined optical signal for transmission from the first node to a second node of the network; transmitting the combined optical signal to the second node via a first optical fiber of an optical fiber connection with a pair of optical fibers between the first node and the second node; separating the first timing signal and the optical data signal in the second node; transmitting a second timing signal from the second node to the first node via the first optical fiber, wherein the first and second timing signals are respective ones of a reference frequency and timing signal and an optical return signal generated in response to the reference frequency and timing signal; receiving the second timing signal at the first node; determining latency information regarding the latency of data transfer between the first node and the second node from a time period that has elapsed between sending the reference frequency and timing signal and receiving of the optical return timing signal, wherein the first node comprises a first optical filter coupled to the first optical fiber and an optical supervisory channel transmitter coupled to the first optical filter for transmitting an optical supervisory channel signal to the first optical fiber, the first optical filter being a bidirectional filter, wherein the second node comprises a second optical filter coupled to the first optical fiber and an optical supervisory channel receiver coupled to the second optical filter for receiving the optical supervisory channel signal, the second optical filter being a bidirectional filter; and using a further optical filter coupled between said first optical filter and said optical supervisory channel transmitter to optically combine the first timing signal with the optical supervisory channel signal, the optical supervisory channel signal and the first timing signal having mutually different wavelengths.