ATL Telecom AM2048 - Manual (Page 11)

ascom
telecom USER GUIDE AM768A/AM2048A
11
Issue 8
Figure 3 Optical System Block Diagram
3.2 Optical Transmission
The optical transmission interface module fits into the same envelope as three copper modules and is
designed to operate over a single optical fibre. This is accomplished using an optical duplexer, which
integrates a laser and a photodiode in a single package. Both directions are transmitted at the
1310nm optical window, leaving the 1550nm window free. The interface module encodes the DSL
framed data using a 5B6B block code for error monitoring and spectral shaping.
Sub-carrier modulation is used to increase the separation between the upstream and downstream
directions. Baseband transmission is used from ELU to NTU, whereas the other direction is
modulated onto a carrier.
For transmission over single-mode fibre, order the AM2048 OS.
For transmission over multi-mode fibre, order the AM2048 OM.
The AM2048A OS and AM2048 OM are Class I products in accordance with EN60825-1 and
therefore inherently safe.
Primary Rate
Interface
ascom
HDSL
Interface
Chip
Micro
Controller
G703
75/120
ohms
User Interface Module
Optical Transmission Module
Laser
Driver
Clock
Recovery
Analogue Rx
and
Channel
Separation
Filter
Optical
Duplexer
ascom
Tranceiver
Codec
Chip