Deck 9: Fiber Optic Coupling and Losses

Question 1

The ratio r = (n1 - n)/ (n1 - n) indicates

A)fresnel reflection
B)reflection coefficient
C)refraction coefficient
D)angular power distribution coefficient

Answer 1

reflection coefficient

Question 2

A GaAs optical source having a refractive index of 3.2 is coupled to a silica fiber having a refractive index of 1.42. Determine Fresnel reflection at interface in terms of percentage.

A)13.4%
B)17.4%
C)17.6%
D)14.8%

Answer 2

14.8%

Question 3

A particular GaAs fiber has a Fresnel reflection magnitude of 17.6% i.e. 0.176. Find the power loss between the source and the fiber?

A)0.86 db
B)0.78 db
C)0.84 db
D)0.83 db

Answer 3

0.84 db

Question 4

Two joined step index fibers are perfectly aligned. What is the coupling loss of numerical aperture are NAR= 0.26 for emitting fiber?

A)-0.828 db
B)-0.010 db
C)-0.32 db
D)0.32 db

Question 5

Two joined graded index fibers that are perfectly aligned have refractive indices ?R=1.93for receiving fiber ?E= 2.15 for emitting fiber. Calculate the coupling loss

A)0.23 db
B)0.16 db
C)0.82 db
D)0.76 db

Question 6

How many types of misalignments occur when joining compatible fiber?

A)one
B)two
C)five
D)three

Question 7

Losses caused by factors such as core-cladding diameter, numerical aperture, relative refractive index differences, different refractive index profiles, fiber faults are known as

A)intrinsic joint losses
B)extrinsic losses
C)insertion losses
D)coupling losses

Question 8

A step index fiber has a coupling efficiency of 0.906 with uniform illumination of all propagation modes. Find the insertion loss due to lateral misalignment?

A)0.95 db
B)0.40 db
C)0.42 db
D)0.62 db

Question 9

A graded index fiber has a parabolic refractive index profile (?=2) and core diameter of 42?m. Estimate an insertion loss due to a 2 ?m lateral misalignment when there is index matching and assuming there is uniform illumination of all guided modes only.

A)0.180
B)0.106
C)0.280
D)0.080

Question 10

Determine coupling efficiency if the misalignment loss in a graded index fiber is 0.102

A)0.136
B)0.898
C)0.982
D)0.684

Question 11

In a single mode fiber, the losses due to lateral offset and angular misalignment are given by 0.20 dB and 0.46 dB respectively. Find the total insertion loss

A)0.66 db
B)0.26 db
C)0.38 db
D)0.40 db

Question 12

The intrinsic loss through a multimode fiber joint is independent of direction of propagation. State whether the given statement is true or false

Question 13

The expanded beam connectors use ____________ for beam expansion and reduction.

A)square micro-lens
B)oval micro-lens
C)spherical micro-lens
D)rectangular micro-lens

Question 14

Lens-coupled expanded beam connectors exhibit average losses of _________ in case of single mode and graded index fibers.

A)0.3 db
B)0.7 db
C)0.2 db
D)1.5 db

Question 15

Sapphire ball lens expanded beam design is successful than spherical lens coupled design.

Question 16

The fiber is positioned at the ________ of the lens in order to obtain a collimated beam and to minimize lens-to-lens longitudinal misalignment effects.

A)aperture
B)focal length
C)curve
D)exterior circumference

Question 17

___________ exhibits a parabolic refractive index profile with a maximum at the axis similar to graded index fiber.

A)lens coupled design
B)sapphire ball lens
C)spherical micro-lens
D)grin-rod lens

Question 18

The GRIN-rod lens can produce a collimated output beam with a divergent angle ?of between _____________ from a light source situated on, or near to, the opposite lens face.

A)1 to 5 degrees
B)9 to 16 degrees
C)4 to 8 degrees
D)25 to 50 degrees

Question 19

In the given equation, if r is the radial distance, n is the refractive index; what does z stands for?

A)focal length
B)distance along the optical axis
C)axial angle
D)diameter

Question 20

The majority of the GRIN-rod lenses have diameters in the range of ____________

A)2 to 2.5 mm
B)3 to 4 mm
C)0.1 to 0.4 mm
D)0.5 to 2 mm

Question 21

Which of the following factors does not cause divergence of the collimated beam from a GRIN-rod lens?

A)lens cut length
B)size of fiber core
C)refractive index profile
D)chromatic aberration

Question 22

GRIN-rod lens connectors have loss characteristics which are independent of the modal power distribution in the fiber.

Question 23

A permanent joint formed between two different optical fibers in the field is known as a

A)fiber splice
B)fiber connector
C)fiber attenuator
D)fiber dispersion

Question 24

How many types of fiber splices are available?

A)one
B)two
C)three
D)four

Question 25

The insertion losses of the fiber splices are much less than the Fresnel reflection loss at a butted fiber joint.