The Fibre Modem provides two separate, optically isolated ports for the Inner Range RS485 LAN. It is used to extend LAN distance, provide immunity to earth loops, and protect against lightning strikes and electrical noise.
Technical Details
Connectivity: Two fibre ports allowing ‘branch’ or ‘loop’ configurations.
Distance Extension:
Multimode: Up to 3km (62.5/125µm 850nm cable, Type ST connectors).
Single Mode: Up to 13km (9/125µm 1300nm cable, Type SC connectors).
Series Connection: Limited by delay unit budget (max 15 delay units between any two modules). Practical examples show up to 8 modems in a daisy-chain.
Isolation: Optical isolation provides electrical separation between LAN segments.
Fault Reporting: ‘Loop Fault’ and ‘Branch Fault’ auxiliary outputs for monitoring.
Installation Environment: 0°C to 50°C (32°F to 122°F), 15% to 85% Relative Humidity (non-condensing). Indoor use only.
Physical Dimensions: 105mm (L) x 94mm (W). 94mm x 94mm with snap-off strip removed. Fibre connector head protrudes 15mm from PCB.
Fault Timeout: Outputs go into alarm after 255 seconds of no data received on the optical port.
Terminal Pinouts
LAN and Power (T1)
Terminal
Label
Function
Connection Notes
T1.1
POS
Power Input (+)
11V-14V DC Input.
T1.2
0V
Power Input (-)
Reference Ground.
T1.3
A
RS485 LAN A
Data A.
T1.4
B
RS485 LAN B
Data B.
Fault Monitoring (T2)
Terminal
Label
Function
Connection Notes
OUT1
C / NO
Port 1 Fault
Closes on Fibre 1 signal loss.
OUT2
C / NO
Port 2 Fault
Closes on Fibre 2 signal loss.
Configuration / Programming
LAN Bias Links: Modems connecting to remote Modules MUST have LAN Bias Links (LK1 & LK2) fitted. Modems connecting directly to a Control Module, a LAN Isolator, or another Fibre Modem (that already has links) must NOT have them fitted.
Monitoring: OUT1 and OUT2 can be wired to Zone Inputs to monitor fibre optic status (e.g., Data Not Detected in Port 1 or 2).
Ancillary LAN (P1): Provides a temporary connection for an LCD/EliteX Terminal when required.
Network Design (Delay Units):
Fibre Modems introduce signal delay. System design must calculate “Delay Units”.
Maximum 15 Delay Units between any two modules (or 14 for a fibre loop).
Calculation: 1 Unit per Fibre Modem + 1 Unit per 1km of Fibre Cable + 1 Unit per 1.35km of twisted pair LAN cable.
Modems are transparent to the RS485 LAN protocol but provide physical layer isolation and extension.
Supports redundant LAN paths when used in a ‘loop’ configuration.
Concept 3000/4000 Note: When measuring LAN A-B voltage on a segment biased by a Fibre Modem (LAN Bias Links fitted), the acceptable range is 200–800mV (not the standard 200–400mV). For LAN Termination in Concept systems, use the Termination Link on connected Modules, or fit a 470 Ohm resistor across LAN A & B if only one Module is connected.
Specifications
Power
Input Voltage: 11-14V DC (from LAN or separate PSU).
Operational Current:
Multimode: 20mA (idle), 120mA (max).
Single Mode: 150mA (idle), 260mA (max).
Power Input Options:
T1 LAN+/0V: Power from LAN or external supply +/-.
P5: 10-way PSU bus cable from Integriti Power Supply.
P3: Ribbon cable from Concept 2A Power Supply.
Fibre Connections
Parameter
Multimode
Single Mode
Connector Type
ST
SC
Fibre Cable
62.5/125µm
9/125µm
Wavelength
850nm
1300nm
TX Optical Power
-12dBm (typ)
-18dBm (min)
RX Sensitivity
-24dBm (min)
-32dBm (min)
Max Modem-to-Modem Distance
3,000m (3km)
13,000m (13km)
LED Indicators
LED
Function
RUN
Flashing = Normal Operation
FAULT
Fibre Optic Port Status (see table below)
RX1 / TX1
Wired LAN data Receive / Transmit. Flashing = Port Active
RX2 / TX2
Optic Port 1 Receive / Transmit. Flashing = Port Active
TX3 / RX3
Optic Port 2 Transmit / Receive. Flashing = Port Active
Fault LED & Output Diagnostics
The FAULT LED and relay outputs (OUT1/OUT2) indicate fibre port status:
Condition
FAULT LED
OUT 1
OUT 2
Data Detected in Both Ports
OFF
Sealed
Sealed
Data Not Detected in Port 1
Fast Flash
Alarm
Sealed
Data Not Detected in Port 2
Slow Flash
Sealed
Alarm
Data Not Detected in Both Ports
ON
Alarm
Alarm
Note: OUT1 and OUT2 have on-board EOL resistors (2k2/6k8 scheme). Wire directly to Zone Inputs — compatible with Integriti, Inception, and Concept platforms.
Earth / Surge Protection
The PCB includes on-board LAN Surge Protection. For effective protection, the EARTH connection must be wired to an effective earth ground.