Most of the existing fiber between our buildings that is in place and working is MMF. I'm running out of fibers. Can I use multiplexers to give me additional strands?
In general, the short answer is "yes." Coarse Wave Division Multiplexers (CWDM), Wave Division Multiplexers (WDM) and Dense Wave Division Multiplexers (DWDM) can be used to increase the effectiveness of existing
infrastructure for both multi-mode fiber (MMF) and single mode fiber (SMF). Assuming that your MMF fiber strands are not already being multiplexed using a CWDM, WDM or DWDM, you would be able to exploit the ability of each of your fiber optic cables to support multiple Lambdas (light wavelengths). Normally, only a single light wavelength is used on a fiber optic strand; however, when you multiplex and run multiple wavelengths concurrently, you effectively create the equivalent of "n" additional new fiber optic strands. How many wavelengths you will be able to get from a fiber optic strand will depend on your budget (i.e., how much you can afford to pay for a multiplexer), type of multiplexing and density or wavelength spacing being used. Take a look at Chapter 5: Fiber Optic Essentials in my book
"Resilient Storage Networks: Designing Flexible Scalable Data Infrastructures"
for additional information on multiplexing, CWDM, WDM and DWDM. Some multiplexer vendors include Adva, Ciena, Cisco, Finisar, Nortel, Pandatel and Sorrento.