ECE 6323 Optical Communications
HW 1
 Han Le - Copyrighted

Name, Student ID

Please do not just copy and paste graphics. Graphics are only used to illustrate certain points, ideas. You should explain your knowledge and understanding of the calculation results.

1. Step-index fiber modes (45 pts)

Use the course Step-Index Fiber App to do the following.
First, select your cladding index to be 1.4xxx where xxx are the last 3 digits of your student ID. Example: if your student ID is 123456789, then it is 1.4789.
Select your core index to be: your cladding index+ 0.05yy where yy are the two digits that precede the last 3 digits of your student ID. Example: if your student ID is 123456789, then yy=56 (right before 789).
Thus, your core=1.4789 +0.0556. 
Select your core radius to be: 2.6zz where zz are the two digits that precede the last 5 digits of your student ID. Example: if your student ID is 123456789, then zz=34 (right before 56789).
Let the wavelength = 1.55 μm.

1.1 (10 pts) Find all the modes of your step-index fiber up to l=5.

Your fiber may or may not have any mode with l=5. It may not even have any mode with l=4. Simply find all modes with  l≤5 . Make sure you list the angular modal number l along with the modal effective index of refraction in a table. You can copy a screenshot of the table in your mode search results. Must explain the results: what does the modal number l imply on the field profile.

1.2 (15 pts) Field profile

For each l from 0 to 3, select the lowest and highest radial modes (if you have only one radial mode, just select that one), plot its ((Subscript[E, comp])^2), E field vector, and H field vector. (Copy and paste - or screen shot is OK). Must explain the results. Discuss the difference between the highest and lowest radial mode.

1.3 (15 pts) Single mode

Keep the cladding index the same. Vary either the core index or core radius or a combination of both such that you have only one mode, i. e. the single-mode condition. Demonstrate and explain your work how the single-mode condition is obtained.

1.4 (5 pts) Cutoff wavelength

Keep the profile as in 1.3 above. Find the cut-off wavelength by increasing the wavelength. Show graphics (screen shot is OK) to demonstrate at which wavelength your waveguide has no mode.

2. Modal dispersion (35 pts)

Use the same profile for single mode as in 1.3 above, vary the wavelength for the following values: 1.6, 1.575, 1.55, 1.525, 1.5 μm. For each wavelength, obtain the modal index of refraction. Then plot the modal index vs. wavelength. This is known as modal dispersion. Show your work sufficiently but compactly, do not just show the dispersion graph.

3. Optical fiber technology (20 pts)

Read the given article:   https://www.wired.com/story/corning-pure-glass-fiber-optic-cable/
Write a ~300-400-word summary of your interests from the article.