Optical Communication - Study Mode

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[#121] Which one of the following fibers has the distinct advantage of low intermodal dispersion?

(A) Multimode step-index fiber

(B) Single-mode step-index fiber

(C) Graded-index multimode fiber

(D) Spatially incoherent multimode fiber

Correct Answer

(B) Single-mode step-index fiber

[#122] An optical link uses a fiber having a power loss of 1 dB/km. A typical photo detector has responsivity 0.5 A/W. If the link is 3 km long and the detector is required to produce a current of 25 µA, the required transmitted power is

(A) 0 dBm

(B) -10 dBm

(C) -30 dBm

(D) -50 dBm

Correct Answer

(B) -10 dBm

[#123] The least attenuation of standard single mode optical fibers are at

(A) 1310 nm

(B) 810 nm

(C) 1500 and 1300 nm

(D) 1550 nm

Correct Answer

(D) 1550 nm

[#124] Coherent radiation in LASER is caused by

(A) Stimulated emission

(B) Spontaneous emission

(C) Temperature increase

(D) Applying large force

Correct Answer

(A) Stimulated emission

[#125] A multimode step index fiber with a core diameter of 80 µm and a relative index difference of 1.5% is operating at a wavelength of 0.85 µm . If the core refractive index is 1.48, then the normalized frequency for the fiber is

(A) 37.9

(B) 75.8

(C) 151.6

(D) 303.2

Correct Answer

(B) 75.8