Subject: OPTICAL COMMUMICTIONS
Branch: Electronics and communication Engineering (ECE) R07
IV B.tech.II semester
Answer any five questions
All Questions carry equal marks
(a) Compare the differences between conventional communication system and optical communication system?
(b) the core of an optical fiber is made of glass of refractive index 1.55 and in clad with another glass of refractive determine,(I) Numerical aperture (II)Acceptance angle (III) Critical angle
(a) Derive the relation between the effective refractive index and normalized propagation constant.
(b) Optical power of 5 mW coupled into optical fiber reduces to 3.8 mW after propagation through a distance of 10 km.Determine the attenuation coefficient of this fiber in dB/Km.Determine the power to be coupled into this is 100 uW of power is to be available at a distance of 85 km/
(a) AGA/AS laser diode has a 600 km cavity length has a effective adsorption coefficient of 15 cm for coated facts, the refractiveness are 0.30 at each end. What is the optical gain at the laser threshold?
(b) If one end of laser is coated with a dielectric reflector so that its reflectivity is now 80%.what is the optical gain at the laser threshold?
(c)If the internal quantum efficiency is 0.6 what is external quantum efficiency in case (a) and (b)?
4. Discuss the magnitude of different dispersion in various fibers and also explain how does this dispersion vary with a different operating wave lengths for the fiber in detail?
(a) Determine the expressions for the power flow through core and cladding of a step index fiber.
(b) Calculate the required delta if a fiber with 8um core and 125 um cladding is to be a single mode at 1300 nm.The core refractive index is 1.5?
(a) what is lasing condition?
(b) Explain the resonating modes of a semiconductors injection laser diode
(a) Write a note on the losses encountered while coupling optical power from an optical fibers into fiber optic receiver?
(b) With neat sketches, explain the principle of operation of an avalanche photo diode.
(a)What is the important of power budget analysis and rice time budget analysis in the design of a fiber optic link?
(b)Write a note on various multiplexing techniques suitable in fiber optic link?