Ciena’s Transparent PDH over Packet Transceivers enable cost-effective transport of T1/E1 streams over packet.The Small Form-factor Pluggable (SFP) modules convert either a T1 or E1 stream into fixed-lengths for transmission over a Packet-Switched Network (PSN). Legacy TDM services can thus be transported over an Ethernet or IP/MPLS network. Frames are transmitted via a 1 Gigabit Ethernet (GbE) port on the host device through one or more PSNs (in the case of multiple operators, for example). At the remote end, the frames are converted back to TDM traffic for handoff as TDM services.