T1 AND E1 FIBER MUXES
10
Table 2-1. Fiber optic characteristics.
Model (Wavelength)
Fiber Type
Transmitter Typical Output Receiver
Typical
Type
Power
Sensitivity
Maximum
Range
T1 Versions
MT1000A-85 (850 nm)
62.5/125 multimode
VCSEL
-18 dBm
-32 dBm
3 km (1.9 miles)
MT1000A-13 (1310 nm)
9/125 single-mode
Laser
-12 dBm
-34 dBm
48 km (29.8 miles)
E1 Versions
MT1000A-E1-85 (850 nm)
62.5/125 multimode
VCSEL
-18 dBm
-32 dBm
4 km (2.5 miles)
MT1000A-E1-13 (1310 nm) 9/125 single-mode
Laser
-12 dBm
-34 dBm
44 km (27.3 miles)
All fiber interfaces offer high performance and have a wide dynamic range, which ensures that the receiver
does not saturate even when using short fiber optic cables. (Saturation is caused when the optical power
applied to the receiver exceeds its maximum allowed input power and results in very high bit error rates.)
2.3.2 C
HANNEL
I
NTERFACE
C
HARACTERISTICS
T1 channel interfaces
The T1 muxes’ channel interfaces meet the requirements of ITU-T Rec. G.703. Each channel port on the T1
models has a 100-ohm (
Ω
) balanced line interface terminated in an RJ-45 eight-pin connector. Line coding is
B8ZS. The nominal balanced interface transmit level is ±2.8 V. The line attenuation is up to 6 dB, and each
T1 signal is processed by an adaptive equalizer that compensates for various cable lengths to ensure optimal
performance. The T1 muxes use phase locked loops (PLL) to recover the clock signals, and the resulting jitter
performance complies with the requirements of ITU-T Rec. G.824, Para. 4.
E1 channel interfaces
As with the T1 models, the channel interfaces on the E1 Fiber Muxes meet the requirements of ITU-T Rec.
G.703. Each channel port on the E1 models has two line interfaces: a 120-ohm (
Ω
) balanced line interface,
terminated in an RJ-45 eight-pin connector, and a 75-ohm unbalanced interface, terminated in two BNC
coaxial connectors. Line coding is HDB3. The nominal balanced interface transmit level is ±3 V, and the
unbalanced interface transmit level is ±2.37 V. The maximum line attenuation is up to 6 dB, and each E1 signal
is processed by an adaptive equalizer that ensures optimal performance by compensating for various cable
lengths. Phase locked loops (PLL) are used to recover the clock signals, and the resulting jitter performance
complies with the requirements of ITU-T Rec. G.823.
Indicators common to both T1 and E1 versions
Each channel interface also has its own set of indicators that show the current state of the channel link. You can
use internal jumpers and switches to disable the alarm indications generated by unused interfaces. AIS data
streams are transmitted instead of failed or unconnected channel data streams.
2.3.3 S
ERVICE
C
HANNEL
The T1 or E1 Fiber Mux provides a full-duplex voice service channel. Operators of two units connected in a
link can communicate over this channel using standard headsets, which connect to sockets on the front panel.
When the local operator wants to speak to the remote operator, a CALL button is used. While this button is
pressed, a CALL indicator lights and an internal buzzer sounds on the remote unit. The proprietary
modulation method used for the service channel doesn’t affect range, and it enables the service channel to
operate independently of payload traffic (as long as the optical signal can be received at the remote end). This
way, operators at both ends can coordinate maintenance activities.