A fibre-coupled etalon used as a telecom channel filter has a free spectral range of…

PHYSICS · Multi-part · Fermi University Physics · Optics & Photonics · Interference and diffraction · Interference and diffraction

What an Instrument Can See, Ch Multiple beams: the stack as a matrix and the etalon as a filter

Problem

A fibre-coupled etalon used as a telecom channel filter has a free spectral range of

2.00

GHz and a finesse of

500

\lambda=1550

nm. ((a)) Give the linewidth

\Delta\nu

, the photon lifetime

\tau_p

, and the quality factor

Q

. ((b)) Estimate the transform-limited bandwidth of a

50

ps input pulse (as

1/\tau_{\text{pulse}}

) and its ratio to the filter's passband width

\Delta\nu

. State whether the pulse can pass through the etalon essentially unchanged.