How do I share an optical drive with Windows?
It would appear tubedogg is correct. Or at least I know of no reason he/she is wrong. HOWEVER, while you may not be able to share the optical drive, it does appear you can share the content (CD or DVD) in the drive. This means you must insert the disk into the optical drive before enabling the sharing of the content with the Windows machine. I have verified this for both a data DVD and music CD.

Setup with Empty Optical Drive on the Mac

The Finder shows the following. The Coelacanth and Marlin are the only visible internal drive partitions on the Mac named Marlin. 



Sharing under System Preferences shows the following. The only shared folders are each user's default public folder. The "File Sharing" box is checked off, as well as, all boxes in the "Options..." popup window. The "DVD or CD Sharing" box is not checked off. 



Note: "Screen Sharing" is only checked off, because the two computers are currently connected using VNC. I verified this has no effect on this answer.

On the Windows PC side, the machine named Shark displays the following. Here, the Mac is already sharing its folders with the Windows PC. The internal drive partitions "Linux HFS+ ESP" and "rEFInd" are flagged as hidden so they did not appear in the Finder window shown above.



Setup after Inserting a Data DVD Into the Optical Drive on the Mac

The DVD now appears in the Finder, as shown below.



I clicked the + symbol and added the DVD to the list of shared folders shown on the Sharing window of the System Preferences. The result is shown below.



This results in the DVD automatically appearing on the Windows machine, as shown below.



I can now open this folder and access the files on the DVD.