Optical Communication

Intermodal dispersion in multimode fibers is minimized with the use of step-index fibers.

Losses in photonic crystal fibers are reduced to a level of . . . . . . . .

Which is the unit of measurement of attenuation in optical fibers?

Dominant intrinsic loss mechanism in low absorption window between ultraviolet and infrared absorption tails is . . . . . . . .

In index-guided photonic crystal fiber structure, the dark areas are air holes. What does white areas suggests?

After Total Internal Reflection the Meridional ray . . . . . . . .

A multimode fiber has RMS pulse broadening per km of 12ns/km and 28ns/km due to material dispersion and intermodal dispersion resp. Find the total RMS pulse broadening.

A multimode step index fiber has a normalized frequency of 72. Estimate the number of guided modes.

Stimulated Raman scattering may have an optical power threshold of may be three orders of magnitude . . . . . . . .

An optical fiber has core-index of 1.480 and a cladding index of 1.478. What should be the core size for single mode operation at 1310nm?

The differential attenuation of modes reduces intermodal pulse broadening on a multimode optical link.

Self-phase modulation can be used for . . . . . . . .

A 4 km optical link consists of multimode step index fiber with core refractive index of 1.3 and a relative refractive index difference of 1%. Find the delay difference between the slowest and fastest modes at the fiber output.

High frequency optical phonon is generated in stimulated Raman scattering.

The phonon is a quantum of an elastic wave in a crystal lattice.

Non-zero-dispersion-shifted fiber was introduced in the year 2000.

Stimulated Brillouin scattering is mainly a . . . . . . . .

A device that reduces the intensity of light in optical fiber communications is . . . . . . . .

A multimode step index fiber has source of RMS spectral width of 60nm and dispersion parameter for fiber is 150psnm -1 km -1 . Estimate rms pulse broadening due to material dispersion.

The fibers which relax the spectral requirements for optical sources and allow flexible wavelength division multiplying are known as . . . . . . . .

Photonic crystal fibers also called as . . . . . . . .

An optical fiber behaves as a birefringence medium due to differences in . . . . . . . .

Any amount of stress occurring at the core-cladding interface would be reduced by grading the material composition.

A single mode fiber has mode field diameter 10.2μm and V = 2.20. What is the core diameter of this fiber?

The periodic arrangement of cladding air holes in photonic band gap fibers provides for the formation of a photonic band gap in the . . . . . . . .

A polarization maintaining fiber operates at a wavelength 1.2μm and have a modal birefringence of 1.8 * 10 -3 . Calculate the period of perturbation.

Which of the following is not related to Kerr effects?

A multimode step-index fiber has a core refractive index of 1.5 and relative refractive index difference of 1%. The length of the optical link is 6 km. Estimate the RMS pulse broadening due to intermodal dispersion on the link.

In waveguide dispersion, refractive index is independent of . . . . . . . .

Practical pulse broadening value for graded index fiber lies in the range of . . . . . . . .

The nonlinear effects in optical fibers are large.

Mie scattering has in-homogeneities mainly in . . . . . . . .

What is refraction?

How many propagation modes are present in single mode fibers?

Self-phase modulation causes modifications to the pulse spectrum.

Rayleigh scattering and Mie scattering are the types of . . . . . . . .

Nonlinear effects which are defined by the intensity - dependent refractive index of the fiber are called as . . . . . . . .

Which is the most important velocity in the study of transmission characteristics of optical fiber?

Most of the power in an optical fiber is transmitted in fiber cladding.

A multimode fiber has refractive indices n1 = 1.15, n2 = 1.11 and an operating wavelength of 0.7μm. Find the radius of curvature?

For suitable power confinement of fundamental mode, the normalized frequency v should be maintained in the range 1.5 to 2.4μm and the fractional index difference must be linearly increased as a square function while the core diameter is linearly reduced to keep v constant. This confinement is achieved by?

Multimode step index fiber has

In graded index multimode optical fiber the refractive index of the core is

Assuming that packet transmission and retransmission can both be described as a Poisson process, calculate the probability that a data packet transmission in an S-ALOHA system will experience a collision with another user. Assume the total traffic rate λ t = 10 packet/sec and the packet duration τ = 10 msec.

Light may be propagated along a fiber-optic cable in which of the following modes?

Which one of the following is the correct statement? The graded index optical fiber cables can be considered to have

A glass fiber has refractive indices n 1 of 1.5 and n 2 of 1. Assuming c = 3 × 10 8 m/s, the multipath time dispersion will be

The normalized frequency of a step index fiber is 28 at 1300 nm wavelength. What is the total number (approx) of guided modes that can be supported by the fiber

In single - mode fibers, how does the fraction of energy travelling through bound mode appears in the cladding?

If n 1 and n 2 are the refractive indices of the core and cladding respectively, the maximum acceptance angle at the air-core interface should be

For a single mode optical cable with 0.25 dB/km loss, the optical power 100 km from a 0.1 mW source will be . . . . . . . .

Numerical aperture is describing the ability of

The distortion in the transmission of carrier frequencies in an underground cable can be eliminated by using

A single mode fiber does not suffer from which type of dispersion?

The sources for fibre optical communication is

The critical angle θ c in an optical fiber is given
by . . . . . . . . Where n 1 is refractive index of medium 1 and n 2 is the refractive index of medium 2.

The configuration used by a line communication system capable of transmitting a data at the rate of 1000 Mbps is

Some of the diffracted light continues down the fiber and some of it escapes through the cladding. The light rays that escape represent a loss in light power which is called

An optical fiber cable laid underground has developed a discontinuity at a distance d from the source end. The fault can be located using the instrument

Raman and Brillouin scattering are usually observed at . . . . . . . .

When light is described as an electromagnetic wave, it consists of a periodically varying electric E and magnetic field H which are oriented at an angle?

Optical fibers suffer radiation losses at bends or curves on their paths.

The modal noise can be reduced by . . . . . . . .

Beat length of a single mode optical fiber is 0.6cm. Calculate the difference between propagation constants for the orthogonal modes.

When three wave components co-propagate at angular frequency w1, w2, w3, then a new wave is generated at frequency w4, which is given by?

A monochromatic wave propagates along a waveguide in z direction. These points of constant phase travel in constant phase travel at a phase velocity Vp is given by?

A single-mode optical fiber has an attenuation of 0.3dB/km when operating at wavelength of 1.1μm. The fiber core diameter is 4μm and bandwidth is 500 MHz. Find threshold optical power for stimulated Brillouin scattering.

The ratio of speed of light in air to the speed of light in another medium is called as . . . . . . . .

Estimate RMS pulse broadening per km due to intermodal dispersion for multimode step index fiber where length of fiber is 4 km and pulse broadening per km is 80.6 ns.

Sharp bends or micro bends causes significant losses in fiber.

A multimode graded index fiber exhibits a total pulse broadening of 0.15μs over a distance of 16 km. Estimate the maximum possible bandwidth, assuming no intersymbol interference.

The scattering resulting from fiber imperfections like core-cladding RI differences, diameter fluctuations, strains, and bubbles is

Who proposed the use of clad waveguide structure?

How the potential macro bending losses can be reduced in case of multimode fiber?

Which equations are best suited for the study of electromagnetic wave propagation?

Polarization modal noise can . . . . . . . . the performance of communication system.

Who proposed the idea of transmission of light via dielectric waveguide structure?

Which thing is more dominant in making a fiber function as a bidirectional optical amplifier?

Light incident on fibers of angles . . . . . . . . the acceptance angle do not propagate into the fiber.

Insertion of a record in a linked list involves the modification of

Which one of the following is the ratio of power lost per unit length to the twice of power transmitted?

Dispersion in an optical fibre used in a communication link is of which type?

The cladding that surrounds the fibre core:

Which optical detector is used when high sensitivity and bandwidth are required?

Which among the following is provided by an optical receiver for the regeneration of data signal with minimum error?

In an optical communication system, having an operating wavelength λ in meters, only X% of its source frequency can be used as its channel bandwidth. The systems is to be used for transmitting TV signal requiring a bandwidth of f Hz. The number of channels transmitted by this system simultaneously is (c = speed of light)

The cut-off wavelength for an optical fibre with 5 µm core diameter and core cladding indices of refraction 1.84 and 1.402 is nearly

Which one of the following statements is NOT true for a step index optical fibre?

In an opto-electronic communication system, the system component in which free electrons are involved in its operation is

Match List-I wish List-II and select the correct answer the correct answer using the options given below: List-I (System) List-II (Order of wavelength) a. Optical fiber communication 1. 10 4 m b. Local television system 2. 10 2 m c. FM broadcasting 3. 10° m d. Satellite 4. 10 -2 m 5. 10 -6 m

In the SONET, form the Synchronous Transport Signal (STS), Optional Carrier (OC) is obtained

A fibre-optic cable has the indices of refraction of core of 1.6 and of cladding of 1.4, For an angle of incidence 70°, the angle of return light ray will be

What type of wiring does ISDN use?

A single-mode optical fiber has a beat length of 8 cm at 1300 nm. The value of birefringence B f will be nearly

The local loop is

Assuming no ISI, the maximum possible bandwidth of a multimode graded index fiber with 5 MHz, shows the total pulse broadening of 0.1s for the distance of about 12 km. What would be the value of bandwidth length product?

An optical fibre has refractive index core

The response time of photodiode depends on

What is/are the advantage(s) of step-index monomode fibre optical cable? 1. Manufacturing process is simple 2. Bandwidth of several GHz-km is possible 3. Splicing is easier Select the correct answer using the options given below:

In an optical fiber, the light beam propagates due to which one of the following?

Which band specifies the operation range of Erbium doped fiber amplifier (EDFA)?

In optical communication, wavelength 1550 nm is used now a days. What is/are the possible reason(s)? 1. Dispersion is very low 2. Loss is very low 3. WDM and optical amplification are feasible Select the correct answer from the options given below:

Attenuation of a narrow monochromatic X-ray beam in a metal plate of thickness d is given by:

Which one of the following instruction is useful while measuring the optical power as a function of wavelength?

A change in the refractive index of a material in response to an applied electric field is called . . . . . . . . effect.

In increasing order of spectral width of three optical sources are

What is the numerical aperture of an optical fiber when its critical angle is 30°

In a step index fibre the refractive index of core n 1 = 1.48 and that of cladding n 2 = 1.45. The numerical aperture of the fiber will be nearly:

The high index contrast enables the PCF core to be reduced from around 8 μmin conventional fiber to . . . . . . . . .

Absorption losses due to atomic defects mainly include . . . . . . . .

The modal noise occurs when uncorrected source frequency is?

An optical fiber has a core radius 2μm and a numerical aperture of 0.1. Will this fiber operate at single mode at 600 nm?

Skew rays follow a . . . . . . . .

What is pulse dispersion per unit length if for a graded index fiber, 0.1μs pulse broadening is seen over a distance of 13 km?

The optical source used for detection of optical signal is . . . . . . . .

The optical source used in a fiber is an injection laser with a relative spectral width $$frac{{{sigma _lambda }}}{lambda }$$ of 0.0011 at a wavelength of 0.70μm. Estimate the RMS spectral width.

$${Gamma _g} = frac{{dx08eta }}{{{C^ * }dk}}.$$ xa0 What is β in the given equation?

Disturbance along the fiber such as vibrations, discontinuities, connectors, splices, source/detectors coupling result in . . . . . . . .

In the design of a single-mode step index optical fiber close to upper cutoff, the single-mode operation is not preserved if

Total internal reflection at the fibre wall can occur only if two conditions are met. One of the condition is the glass inside the fibre core must have a/an . . . . . . . . index of refraction than/as the index of refraction of the material surrounding the fibre core.

Which one of the following fibers has the distinct advantage of low intermodal dispersion?

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

The least attenuation of standard single mode optical fibers are at

Coherent radiation in LASER is caused by

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

Consider the following advantages of optical fiber-cables: 1. Small diameter 2. Immunity to cross talk and electromagnetic interference 3. Laser and LED modulation methods lend themselves ideally to digital operation. Which of these advantages are correct?

What is the device used for measuring the power in an optical signal?

Polarization mode dispersion (PMD) is mainly observed in

Which one of the following statement is correct? The model noise in multimode fibers cannot be reduced by

For a photo-diode with responsivity of 0.50 A/W & optical power of about 12 µW, what would be the value of generated photocurrent?

Generally, the SM fiber will have a core diameter of

Optical storage devices employ

For a silica fiber the refractive index of core layer is 1.56 and that of cladding is 1.35. Calculate numerical aperture

The bandwidth of the optical signal having a rise time (response time) t r is 500 MHz. Find the value of rise time.

The modal dispersion in a fiber is 20 ns/km. What will be the overall pulse spread in 10 km long fiber? Assume material dispersion to be zero

Which is the transmission medium for VLF electromagnetic waves especially applicable for aeronautical and submarine cables?

When the mean optical power launched into an 8 km length of fiber is 120 µW. The mean optical power at the fiber output is 3 µW. Find the signal attenuation

Not an example for actuator

An optical fiber communication system works on a wavelength of 1.3 µm. The number of subscribers it can feed, if a channel requires 20 kHz, is

Approximately what is the frequency limit of an optical fiber?

On which bands, do the optical fibers operate? 1. Ultra violet band 2. Ultra high frequency band 3. Visible light band 4. Infrared band Select the correct answer from the options given below:

Numerical aperture is closely related to acceptance angle and is the figure of merit commonly used to measure

The Bragg's Law of X-ray diffraction is:

For a 3-µm-diameter optical fiber with core and cladding indexes of refraction of 1.545 and 1.510, respectively. The cut off wavelength is.

Sensitivity of optical receivers is measured in

If a light travels in a certain medium and it gets reflected off an optically denser medium with high refractive index, then it is regarded as . . . . . . . .

In a optical fiber, the refractive index of the cladding material should be

. . . . . . . . is used to describe the light gathering or light collecting ability of an optical fiber

A step index fibre has core diameter 40 µm with core refractive indix of 1.3 and numerical aperture 0.5, then the refractive index of cladding is

Refractive index of glass is 1.5. What is the wavelength of a beam of light with a frequency of 10 14 Hz in glass? Assume velocity of light in vacuum to be 3 × 10 8 m/sec.

The concept used in the scheme of WDM is similar to

Which of the following introduces mode partition noise?

The working of an optical fiber is bases on

If a fiber operates at 1400 nm with the diameter of about 10 µm, n 1 = 1.30, ∆ = 0.80%, V = 3.5, then how many modes will it have?

Fibers have numerical aperture (NA) in the region of 0.15 to 0.4. Fibers with higher N.A. values generally exhibit

The fiber splice is a . . . . . . . . joint between 2 fibers.

At critical radius of curvature, in multimode fibers

Modern day optical fibers have losses of the order of

Copper-network can be converted to fibre optics by using

In an optical fiber, the pulse dispersion effect is minimized by 1. Using a high frequency light source 2. Using plastic cladding 3. Minimizing the core diameter Which of the above statements is/are correct?

In single mode fibers, the most beneficial index profile is

The typical core dimensions of single mode step-index fiber is

Identify the false statement for interferomatric method:

In an optical fibre, if the total internal reflection takes place, which of the following conditions have to be satisfied?

Non-linear Cross Phase Modulation (XPM) occurs due to

The Dispersion Shifted fiber is normally designed to have zero chromatic dispersion at

An optical fibre has a reflective index of 1.641 for the core and 1.422 for the cladding. The critical angle above which the ray will be totally internally reflected is:

When the input and output power in an optical fiber is 120μW & 3μW respectively and the length of the fiber is 8 km. What is the signal attenuation per km for the fiber?

What is the unit of normalized frequency?

What does ISI stand for in optical fiber communication?

Which law gives the relationship between refractive index of the dielectric?

The variant of non-zero-dispersion-shifted fiber is called as . . . . . . . .

. . . . . . . . zsemiconductor laser sources generally have broader bandwidths.

Which of the following statements best explain the concept of material absorption?

How many mechanisms are there which causes absorption?

In the given equation, state what αr suggests?

For no overlapping of light pulses down on an optical fiber link, the digital bit rate BT must be . . . . . . . .

The light sources used in fibre optics communication are . . . . . . . .

Which of the following is not a metallic impurity found in glass in extrinsic absorption?

What is dispersion in optical fiber communication?

A step-index fiber has core refractive index 1.46 and radius 4.5μm. Find the cutoff wavelength to exhibit single mode operation. Use relative index difference as 0.25%.

The phenomenon which occurs when an incident wave strikes an interface at an angle greater than the critical angle with respect to the normal to the surface is called as . . . . . . . .

Constructive interference occur when total phase change after two successive reflections at upper and lower interfaces is equal to? (Where m is integer)

One of the given statements is true for intermodal dispersion. Choose the right one.

Consider a single mode fiber having core refractive index n1 = 1.5. The fiber length is 12m. Find the time taken by the axial ray to travel along the fiber.

A single-mode step-index fiber or multimode step-index fiber allows propagation of only one transverse electromagnetic wave.

Numerical aperture is constant in case of step index fiber.

What is the numerical aperture of the fiber if the angle of acceptance is 16 degree?

Rayleigh scattering can be reduced by operating at smallest possible wavelengths.

Intermodal dispersion occurring in a large amount in multimode step index fiber results in . . . . . . . .

A graded-index fiber has a core with parabolic refractive index profile of diameter of 30μm, NA=0.2, λ=1μm. Estimate the normalised frequency.

The dispersion due to material, waveguide and profile are -2.8nm -1 km -1 , 20.1nm -1 km -1 and 23.2nm -1 km -1 respectively. Find the total first order dispersion?

When two components are equally excited at the fiber input, then for polarization maintaining fibers δΓg should be around . . . . . . . .

3dB optical bandwidth is always . . . . . . . the 3dB electrical bandwidth.

What is needed to predict the performance characteristics of single mode fibers?

The beat length in a single mode optical fiber is 8 cm when light from a laser with a peak wavelength 0.6μm is launched into it. Estimate the modal birefringence.

The difference between the modes' refractive indices is called as . . . . . . . .

A single mode fiber has refractive indices n1=1.50, n2 = 2.23, core diameter of 8μ m , wavelength = 1.5μ m cutoff wavelength = 1.214μ m . Find the radius of curvature?

0.4 dB/km, 1.4μm, 6μm, 550MHz. Find threshold optical power for stimulated Raman scattering.

A single mode fiber has a zero dispersion wavelength of 1.21μm and a dispersion slope of 0.08 psnm -2 km -1 . What is the total first order dispersion at wavelength 1.26μm.

Linear scattering effects are . . . . . . . . in nature.

For many applications that involve optical fiber transmission, an intensity modulation optical source is not required.

Which equation is used to calculate MFD?

. . . . . . . . results from a case of nonlinear dispersion compensation in which the nonlinear dispersion compensation in which the nonlinear chirp caused by self-phase modulation balances, postpones, the temporal broadening induced by group velocity delay.

When λ is the optical wavelength in vacuum, k is given by $$k = frac{{2pi }}{lambda }.$$xa0 What does k stand for in the

An alternative modification of the dispersion characteristics of single mode fibers involves achievement of low dispersion gap over the low-loss wavelength region between . . . . . . . .

Digital transmission is more likely to be affected by modal noise.

The beating between light at different frequencies or wavelengths in multichannel fiber transmission causes . . . . . . . .

How many categories of nonlinear effects are seen in optical fibers?

Chromatic dispersion is also called as intermodal dispersion.

Conventional optical fibers has more transmission losses than photonic crystal fibers.

The in-homogeneities in Mie scattering can be reduced by coating of a fiber.

Meridional rays in graded index fibers follow . . . . . . . .

Dispersion-shifted single mode fibers are created by . . . . . . . . .

A decibel may be defined as the ratio of input and output optical power for a particular optical wavelength.

Stimulated Raman scattering occur in . . . . . . . .

A single mode fiber has a beat length of 4cm at 1200nm. What is birefringence?

Velocity of light travelling in an optical fibre is

In an optical fiber, dispersion:

Multimode graded index fibers are manufactured from materials with

Which one of the following is capable of giving the highest data speed?

Maximum data rate of a channel for a noiseless 2-kHz binary channel is-

A digital optical fiber communication system operating at a wavelength of 1 µm requires a maximum bit error rate of 10 -9 . What is the theoretical quantum limit at the receiver in terms of the quantum efficiency of the detector and the energy of an incident photon?

Match List-I with List-II and select
the correct answer using the options given below: List-I (Different Fibre Generation) List-II (Optical Components Used) a. First 1. Graded index multimode fibre and 1310 nm LD b. Second 2. Graded index multimode fibre and 850 nm LD c. Third 3. Step index monomode fibre and 1550 nm LD d. Fourth 4. Step index monomode fibre and 1310 nm LD

The cladding which surrounds the fibre core

A certain optical fiber has refractive index of clad (n 1 ) = 1.40 and that of core (n 2 ) = 1.05. Its numerical aperture will be

Losses in optical fibers can be caused by

Splice is

In an optical fiber communication system, which among the following is not a typical transmitter function?

The noise factor of an attenuator pad that has an insertion loss of 6 dB is

Optical fibers are preferred as communication links for Lasers because they:

In optical communication, the maximum angle in which external light rays may strike the air/glass interface and still propagate down the fiber is called as

Optical carrier frequency is in the range of

In Kerr effect, induced index change is directly proportional to the . . . . . . . .

The multimode graded index fiber exhibits total pulse broadening of 0.1 µsec over a distance of 15 Km. The length - Bandwidth product of the fiber is

Multimode graded index fibers have overall buffer jackets same as multimode step index fibers but have core diameters

Most of the optical power is carried out in core region than in cladding.

The . . . . . . . . . ray passes through the axis of the fiber core.

For lower bandwidth applications . . . . . . . .

If the input power 100μW is launched into 6 km of fiber, the mean optical power at the fiber output is 2μW. What is the overall signal attenuation through the fiber assuming there are no connectors or splices?

The effects of intrinsic absorption can be minimized by

The optical fiber incurs a loss in signal power as light travels down the fiber which is called as . . . . . . . .

When a ray of light enters one medium from another medium, which quality will not change?

The maximum bit rate that may be obtained on an optical fiber link is 1/3Γ.

What is different in case of cross-phase modulation from self-phase modulation?

Plastic fibers are less widely used than glass fibers.

Single mode fibers allow single mode propagation
the cladding diameter must be at least

Which one of the following specifications does not fit for a single-mode fiber?

The index profile of a core of multimode graded index fiber is given by?