The GATE Grind

GATE Communication and Optical Instrumentation: Interferometry and fiber-optic sensing – Previous Year Questions

6 GATE previous year questions on Interferometry and fiber-optic sensing (Communication and Optical Instrumentation, Instrumentation Engineering) with answers and explanations, from every paper.

  1. GATE 2021 IN Q32 (1 mark, Numerical answer) – A Michelson interferometer’s movable arm is displaced 325 μm in vacuum (n = 1), and 1000 fringes cross the observation point. The laser wavelength is…
  2. GATE 2021 IN Q65 (2 marks, Numerical answer) – A large multimode fibre has n core=1.5 and n clad=1.2. A section with cladding removed passes through a liquid of index n liquid. An LED illuminates…
  3. GATE 2022 IN Q39 (2 marks, Multiple choice) – A car moves collinearly with a transceiver’s laser beam. A pulse emitted at t=0 returns after reflection from the car 100 ns later. A second pulse…
  4. GATE 2023 IN Q45 (2 marks, Numerical answer) – A silica-glass fibre has core index 1.47 and cladding index 1.44. The cladding is completely stripped off and the core immersed in water of index…
  5. GATE 2025 IN Q55 (2 marks, Numerical answer) – The shown Michelson interferometer measures a gas refractive index. Its transparent chamber contains gas of index n g1 at atmospheric pressure. A 532…
  6. GATE 2026 IN Q64 (2 marks, Numerical answer) – For a fiber Bragg grating-based sensor, the shift in the Bragg wavelength gives information about the value of the measurand. For a Bragg wavelength…