Single – Frequency Injection Lasers

Optical Communications

This set of Optical Communications Multiple Choice Questions & Answers (MCQs) focuses on ” Single Frequency Injection Lasers”.

1. __________________ may be improved through the use of frequency-selective feedback so that the cavity loss is different for various longitudinal modes.
a) Frequency selectivity
b) Longitudinal mode selectivity
c) Electrical feedback
d) Dissipated power

2. Device which apply the frequency-selective feedback technique to provide single longitudinal operation are referred to as ________________
a) DSM lasers
b) Nd: YAG lasers
c) Glass fiber lasers
d) QD lasers

3. Which of the following does not provide single frequency operation?
a) Short cavity resonator
b) DSM lasers
c) Coupled cavity resonator
d) Fabry-Perot resonator

4. A method for increasing the longitudinal mode discrimination of an injection laser which is commonly used?
a) Decreasing refractive index
b) Increasing the refractive index
c) Increasing cavity length
d) Shortening of cavity length

5. Conventional cleaved mirror structures are difficult to fabricate with the cavity lengths below __________
a) 200 μm and greater than 150 μm
b) 100 μm and greater than 50 μm
c) 50 μm
d) 150 μm

6. In the given equation, corrugation period is given by lλb/2Ne. If λb is the Bragg wavelength, then what does ‘l’ stand for?
a) Length of cavity
b) Limitation index
c) Integer order of grating
d) Refractive index

7. The first order grating (l=1) provide the strongest coupling within the device.
a) True
b) False

8. The semiconductor lasers employing the distributed feedback mechanism are classified in _________________ categories.
a) One
b) Two
c) Three
d) Four

9. DBF-BH lasers exhibit low threshold currents in the range of ________________
a) 40 to 50 mA
b) 21 to 30 mA
c) 2 to 5 mA
d) 10 to 20 mA

10. Fabry-Perot devices with BH geometries high modulation speeds than DFB-BH lasers.
a) True
b) False

11. The InGaAsP/InP double channel planar DFB-BH laser with a quarter wavelength shifted first order grating provides a single frequency operation and incorporates a phase shift of ______________
a) π/2 Radians
b) 2π Radians
c) π Radians
d) 3π/2 radians

12. The narrow line-width obtained under the CW operation for quarter wavelength shifted DFB laser is ________________
a) 2 MHz
b) 10 MHz
c) 3 MHz
d) 1 MHz

13. Line-width narrowing is achieved in DFB lasers by a strategy referred as _______________
a) Noise partition
b) Grating
c) Tuning
d) Bragg wavelength detuning

14. _________________ is a technique used to render the non-conducting material around the active cavity by producing permanent defects in the implanted area.
a) Dispersion
b) Ion de-plantation
c) Ion implantation
d) Attenuation

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