I think if it was in reference to a fiber optic then it would be in a section of fiber optic or it would state fiber optic. Without knowing the section I am guessing it means a lighting circuit. Is this referencing art 725?What is meant when the NEC references electric light circuit? Is this a reference to a lighting circuit or a fiber optic reference?
I did a search of the phrase "electric light circuit" in the 2011 NEC and found no such phrase.
Here's the sentence from Mike's book, "Audio output circuits [640.9(C)] using Class 2 or Class 3 wiring methods [725.136 and 725.154] aren't permitted in any enclosure, raceway, or cable with conductors of electric light or power circuits."