Lecture 14Analysis of Midterm Exam.

First Generation Optical NetworksFirst Generation Optical Networks.

Slide 1Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14

Fall 2008 ECE 5870 Midterm ExamOpen books, open notes

1 (6 pt) By controlling temperature of the heatsink of a DFB laser the bandgap of its active zone and1. (6 pt) By controlling temperature of the heatsink of a DFB laser, the bandgap of its active zone and thus the quantum energy of the emitted light are tuned within 5meV. Assuming the longest wavelength within the tuning range is 1550nm, find the shortest wavelength. How many ITU WDM channels on the 100GHz grid can be covered by such lasers?

2. (6 pt) Multimode index-step fibers designed for high-power application (not for telecommunication) have large numerical aperture approaching values as high as 0.37. The fiber has a pure fused silica core (n ≈ 1.46) and a hard polymer cladding. Find maximum acceptance angle of the fiber. Find the maximum angle for the rays propagating inside the fiber core Find the index of refraction of themaximum angle for the rays propagating inside the fiber core. Find the index of refraction of the polymer cladding. Assuming the tolerance factor ε = ½, find the bit rate - length product for this fiber.

3 (6 pt) When an unchirped Gaussian pulse with T = 10ps is launched into a fiber it becomes twice3. (6 pt) When an unchirped Gaussian pulse with T0 = 10ps is launched into a fiber, it becomes twice longer at the fiber end. Find the pulsewidth at the end of the same fiber if unchirped pulse at the input has T0 = 12.5ps.

4 (6 pt) A Fabry Perot filter has one of its transmission peaks at 1500nm another at 1200nm and two4. (6 pt) A Fabry-Perot filter has one of its transmission peaks at 1500nm, another at 1200nm, and two peaks in between. Find resonant wavelengths of those two peaks.

5. (6 pt) A photo-receiver operates at such a level of the optical input that the intensity of shot noise in bit 1 is 8 times stronger than intensity of the thermal noise: σ 2 = 8σ 2 The bit error rate at this

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 2

bit 1 is 8 times stronger than intensity of the thermal noise: σs = 8σth . The bit error rate at this condition was found to be BER = 2.1⋅10-10, and the thermal noise was estimated to be 0.5μA. Find photocurrent in bit 1 and the current corresponding to the optimal decision level.

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 3

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 4

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 5

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 6

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 7

Fi t G ti O ti l N t kFirst Generation Optical Networks

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 8

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 9

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 10

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 11

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 12

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 13

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 14

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 15

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 16

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 17

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 18

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 19

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 20

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 21

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 22

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 23

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 24

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 25

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 26

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 27

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 28

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 29

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 30

Ivan Avrutsky, ECE 5870 Optical Communication Networks, Fall 2008, Lecture 14 Slide 31