Application of VCSELs in next-generation telescope array networks such as the Square Kilometre array

Abstract

The distribution of precise and accurate optical clock signals across fibre links has a significant impact in various fields. Many applications require the transfer of stable and precise timing signals from a single central location to multiple remote users via a fibre network. One such application is the big data instrument, the Square Kilometre Array (SKA). An increase in demand for more bandwidth by broadband providers has prompted the expansion and development of attractive and intelligent, modern communication networks. Vertical cavity surface-emitting lasers (VCSELs) are an attractive solution and a potential candidate for realizing low cost and high bandwidth data transmission. In this paper a novel and unique, all-optical technique for measuring the one-way transmission time delay of the propagating signal along an optical fibre is presented. This has been successfully achieved by optically injecting a pulse-per-second (PPS) signal into the secondary mode of a 1550 nm VCSEL located at the client end. A round-trip latency time of 113.2 μs was experimentally measured over a 22 km G.652 single mode fibre (SMF). A novel VCSEL capacity upgrade technique is further demonstrate. This was experimentally achieved by simultaneously modulating a single 1310 nm VCSEL with a 10 Gbps 27 − 1 pseudorandom binary sequence (PRBS) and a polarization based PPS clock signal. An error free transmission over 11 km of G.652 SMF was reported, with a measured transmission penalty of 0.52 dB when the VCSEL was simultaneously modulated with the 27 − 1 PRBS and the polarization based PPS signal.