Questions without answers in Communication and Optical Instrumentation

An analog speech signal contains signals from $200$ $\mathrm{Hz}$ to $2400$ $\mathrm{Hz}$. It is sampled at $6$ $\mathrm{kHz}$ and quantized with $512$ levels for pulse c...

The slope efficiency of a laser diode is $0.5 \mathrm{~W} / \mathrm{A}$, and the output optical power at a current of $100$ $\mathrm{mA}$ is $30$ $\mathrm{mW}$. Assuming ...

An amplitude modulated voltage signal $x(t)$ drives a load of $1 \Omega$.$$x(t)=K \cos (300 \pi \: t)+L \cos (240 \pi \: t)+L \cos (360 \pi \: t) .$$If the efficiency is ...

For a fiber Bragg grating-based sensor, the shift in the Bragg wavelength gives information about the value of the measurand. For a Bragg wavelength of $1550$ $\mathrm{nm...

A schematic of a Michelson interferometer, used for the measurement of refractive index of gas, is shown in the figure. The transparent chamber is filled with a gas of re...

A silica-glass fiber has a core refractive index of $1.47$ and a cladding refractive index of $1.44.$ If the cladding is completely stripped out and the core is dipped in...

A sinusoidal carrier wave with amplitude $A_{c}$ and frequency $f_{c}$ is amplitude modulated with a message signal $m(t)$ having frequency $0 < f_{m} \ll f_{c}$ to gener...

An amplitude modulation $\text{(AM)}$ scheme uses tone modulation, with modulation index of $0.6$. The power efficiency of the $\text{AM}$ scheme is ______________ $\%$ (...

When the movable arm of a Michelson interferometer in vacuum $(n=1)$ is moved by $325\: \mu m$ , the number of fringe crossings is $1000$. The wavelength of the laser use...

A laser pulse is sent from ground level to the bottom of a concrete water tank at normal incidence. The tank is filled with water up to $\text{2 m}$ below the ground leve...

In the figure shown, a large multimode fiber with $n_{\text{core}}=1.5$ and $n_{\text{clad}}=1.2$ is used for sensing. A portion with the cladding removed passes through ...

A laser beam of 10 mm beam diameter is focused onto an optical fiber using a thin biconvex lens as shown in the figure. The refractive index of the lens is $1.5$. The ref...

As shown in the figure, a slab of finite thickness $t$ with refractive index $n_2=1.5$, has air $(n_1=1)$ above and below it. Light of free space wavelength $600 nm$ is i...

In a sinusoidal amplitude modulation scheme (with carrier) the modulated signal is given by $A_m(t)=100\cos(\omega_ct) +50\cos(\omega_mt)\cos(\omega_ct)$, where $\omega_c...

An angle modulated signal with carrier frequency $\omega_c=2\pi\times10^6\;rad/s$ is given by $\varphi_m(t)=\cos(\omega_ct+5\sin(1000\pi t)+10\sin(2000\pi t))$. The maxim...

In a single-mode optical fiber, the zero-dispersion wavelength refers to the wavelength at which the material dispersion is zero.waveguide dispersion is zero.sum of mater...

A pulsed laser emits rectangular pulses of width 1 nanosecond at a repetition rate of 1kHz. If the average power output is 1 mW, the average power over a single pulse dur...

Consider a Michelson interferometer as shown in the figure below. When the wavelength of the laser light source is switched from 400 nanometer to 500 nanometer, it is obs...

The resolving power of a spectrometer consisting of a collimator, a grating and a telescope can be increased byincreasing the angular magnification of the telescopeincrea...

A full duplex binary $FSK$ transmission is made through a channel of bandwidth $10\;kHz$. In each direction of transmission the two carriers used for the two states are s...

Monochromatic light from a step index $(n_1=1.500;n_2=1.485),$ multimode optical fiber of core diameter $100\;\mu m$ is incident through air $(n=1.000)$ onto a linear pho...

Signals from fifteen thermocouples are multiplexed and each one is sampled once per second with a 16-bit $ADC$. The digital samples are converted by a parallel to serial...

The double convex lens is used to couple a laser beam of diameter $5\;\text{mm}$ into an optical fiber with a numerical aperture of $0.5$. The minimum focal length of the...

The responsivity of the $\text{PIN}$ photodiode shown is $0.9\;A/W.$ To obtain $V_\text{out}$ of $-1\;\text{V}$ for an in optical power of $1\;\text{mW},$ the value of $R...

Light of wavelength $630\;\text{nm}$ in vacuum, falling normally on a biological specimen of thickness $10\;\mu\text{m}$, splits into two beams that are polarized at righ...

An $\text{LED}$ emitting at $1\;\mu\text{m}$ with a spectral width of $50\;\text{nm}$ is used in a Michelson interferometer. To obtain a sustained interference, the maxim...

A multi-mode optical fiber with a large core diameter has a core refractive index $n_1 = 1.5$ and cladding refractive index $n_2 = 1.4142.$ The maximum value of $\theta_A...

A Michelson Interferometer using a laser source of wavelength $\lambda_0 = 500\; nm$, with both the mirrors $(M_1$ & $M_2)$ fixed and positioned equidistant from the spl...

An amplitude modulated signal is shown in the figure. The modulation index is(up to one decimal place) $\_\_\_\_\_$

An optical pulse containing 6 x 10$^6$ photons is incident on a photodiode and 4.5 x 10$^6$ electron-hole pairs are created. The maximum possible quantum efficiency (in %...