Distribution of reference frequency and timing information in a network involves determining latency between a first and second node from time delay between transmission of a reference frequency and timing signal and reception of an optical return timing signal in response. 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, provisions are made to transmit the reference frequency and timing signal and the resulting optical return signal via the same fiber, one in the same direction as the unidirectional data signal over that fiber and the other upstream. Repeaters between the nodes may be modified to pass such signals upstream and downstream. In an embodiment wherein the network provides for an optical supervisory channel, the optical filters for combining the optical supervisory channel signal with the unidirectional data signal and separating the optical supervisory channel signal from the unidirectional data signal are used to combine and separate the reference frequency and timing signal and to pass the optical return timing signal. For this purpose, further optical filters may be added outside the main optical data channel to combine and separate the reference frequency and timing signal and the optical supervisory channel and to pass the optical return signal back to the filter that separates the optical supervisory channel signal from the data signal.