Statistical analysis of subcarrier-modulated transmission over 300 m of 62.5-/spl mu/m-core-diameter multimode fiber

Abstract

We simulate subcarrier-modulated (SCM) transmission over 300 m of 62.5-/spl mu/m-core-diameter multimode fiber (MMF) using 1300-nm edge-emitting lasers and 850-nm vertical-cavity surface-emitting lasers (VCSELs) for beam offsets from 0 to 30 /spl mu/m. We model 81 "worst-case" fibers while scaling their bandwidth according to a differential modal delay (DMD) criterion of 2 ns/km for our analysis at a center wavelength of 1300 nm and a DMD of 4 ns/km for analysis at 850 nm, all in order to ensure that the worst 5% of the MMF is being modeled as per the Gigabit Ethernet standard. We consider SCM carrier frequencies from 1 to 9 GHz at data rates of 1.25 and 2.5 Gb/s. Results show that SCM transmission with eye-opening penalties (EOPs) below 3 dB is achievable at 2.5 Gb/s for both edge-emitting lasers and VCSELs. VCSELs are found to be better suited for center launch than offset launch while edge-emitting lasers are better suited for offset launch at radial offsets of 17 to 23 /spl mu/m. The region of best performance for VCSELs under offset launch is from radial offsets of 17 to 30 /spl mu/m at carrier frequencies of 0 to 8 GHz, over which we observed an EOP less than 5 dB, while for edge-emitting lasers we observed a region of best performance from 10 to 25 /spl mu/m over carrier frequencies from 2.5 to 9 GHz. This means that if interchannel crosstalk was ignored, a theoretical aggregate maximum bit rate for VCSELs of /spl sim/ 7.5 Gb/s should be achieved for three channels using a single offset launch between 17 and 30 /spl mu/m for a fiber length of 300 m in order to achieve an EOP less than 5 dB for each channel. For edge-emitting lasers, the theoretical maximum is /spl sim/ 5 Gb/s for two channels with each having an EOP of less than 3 dB for transmission over a fiber of length 300 m. We also demonstrate how SCM performance is influenced by the usable average slope (UAS) of the frequency response: a UAS greater than 0.6/spl times/10/sup -8/ dB/Hz implies severe deterioration of SCM performance.