Ethernet is random access channel. There are packet collision and detection and avoidance. But TDMA, users transmit with in well defined slots hence no collision.
OC1 is WDMA not FDMA.
Yes, T1 may be considered as WAN
CDMA is more suitable for wireless environment. Optical CDMA is coming up for optical network. Computer networks have generally ring or star or bus architecture. CDMA requires a bandwidth that is much larger than avalable on these days copper link used for computer networking.
Broadband Communication is for transmitting applications that require large bandwidth like video and high speed data. Mostly for mulimedia transmission.