Aspects of the present disclosure are directed to alternative repeater design(s) that advantageously improve signal-to-noise of distributed acoustic sensing (DAS) systems using coherent detection of Rayleigh backscatter in multi-span links including inline amplification that may be employed—for example—in undersea submarine systems. The repeater designs incorporate Rayleigh combine units (RCU) and Rayleigh drop units (RDU) to reduce Rayleigh backscatter loss as Rayleigh signal(s) is/are routed to a link that propagates the backscatter signal in an opposite direction relative to interrogation pulse(s).

A repeater device that can achieve signal transferring and path switching in optical transmission lines susceptible to environmental changes is provided. The repeater device receives weak signal light and normal reference light and transmits them in a communication network. The repeater includes: an optical route selector that selects an input-side spatial link connected to an upstream adjacent node and an output-side spatial link connected to a downstream adjacent node; a link state detector that detects a link state of at least one of the input-side spatial link and the output-side spatial link, wherein the link state is an attenuation rate or a transmission rate; and a controller that controls the optical route selector to select an optimal pair of output-side spatial link and input-side spatial link according to the link state.

Aspects of the present disclosure are directed to alternative repeater design(s) that advantageously improve signal-to-noise of distributed acoustic sensing (DAS) systems using coherent detection of Rayleigh backscatter in multi-span links including inline amplification that may be employedfor examplein undersea submarine systems. The repeater designs incorporate Rayleigh combine units (RCU) and Rayleigh drop units (RDU) to reduce Rayleigh backscatter loss as Rayleigh signal(s) is/are routed to a link that propagates the backscatter signal in an opposite direction relative to interrogation pulse(s).

The disclosure includes a multiplexed telecommunication-band quantum network that utilizes atomic arrays in optical cavities. An example quantum networking system includes at least one quantum repeater node. The quantum repeater node includes an array of neutral atoms disposed in an optical cavity and a fiber-optic switch (FOS). The FOS is optically coupled to the optical cavity. The quantum repeater node also includes at least one beamsplitter. The at least one beamsplitter is optically coupled to the FOS.

A repeater device that can achieve signal transferring and path switching in optical transmission lines susceptible to environmental changes is provided. The repeater device receives weak signal light and normal reference light and transmits them in a communication network. The repeater includes: an optical route selector that selects an input-side spatial link connected to an upstream adjacent node and an output-side spatial link connected to a downstream adjacent node; a link state detector that detects a link state of at least one of the input-side spatial link and the output-side spatial link, wherein the link state is an attenuation rate or a transmission rate; and a controller that controls the optical route selector to select an optimal pair of output-side spatial link and input-side spatial link according to the link state.