Patent ID: 8582769

Claim:
A secure communication system, comprising a first wavelength-division multiplexing passive optical network (WDM-PON) to perform quantum encryption, the first WDM-PON providing quantum channels for quantum encryption; and a synchronization device having a second WDM-PON to synchronize with the first WDM-PON and to provide separate classical channels for data communication, a server coupled to the first and second WDM-PONs; and computer readable storage medium configured with a program to determine length difference for fibers connecting the server and different users, where for m users, each user is connected with the server via a fiber link l i (iε[1,m]), and ∀iε[1,m−1], l i <l i+1 : T ⁡ ( l ) = 2 ⁢ l nc , where l is a length of fiber connecting the server and a user, n is a refractive index of fiber, and c is a speed of light, and T(l i ) represents a round-trip time for a signal to travel between the server and i th user.