IDM-NT008 Desktop 8-Channel Telephone Optical Multiplexer

The IDM-NT008 desktop 8-channel multi-service optical multiplexer is a desktop integrated service optical fiber access device developed by Beijing Ruiguang Jiyuan Digital Technology Co., Ltd.; it provides 8 telephone interfaces to the user side through 1 optical fiber channel and is used for point-to-point optical fiber subscriber line provisioning. The product demonstrates the flexible capability of the optical multiplexer at the access layer. The device extends voice services to various user areas, achieving cross-boundary line extension and serving as a substitute for remote small offices and deferred switching offices; it is also used in urban areas to address the limitations of twisted pair in terms of frequency band and transmission distance. As a professional optical multiplexer manufacturer, Raytrans offers this multi-service optical multiplexer and telephone optical multiplexer product for wide application in scenarios such as government private network optical fiber communication solutions, and the Raytrans brand series of optical multiplexers continues to provide reliable access for various private network communications.

Key specifications at a glance: 8 FXO/FXS telephone channels · 4 8P8C RJ45 connectors (2 channels per port: pins 4/5 for the first channel and pins 3/6 for the second channel) · single fiber 3040km · FC optical port by default · audio 300Hz3400Hz · ITU G.711 A-law · compact desktop size

What Kind of Device Is the 8-Channel Multi-Service Optical Multiplexer?

The IDM-NT008 desktop 8-channel multi-service optical multiplexer is designed with dedicated large-scale integrated circuits and completes the connection between subscriber terminals or between subscriber terminals and the public switched telephone network through the optical fiber transmission medium. As a mature multi-service optical multiplexer product, a single unit provides 8 telephone channels, supports FXO and FXS interfaces, can connect 8 ordinary telephones, and can also provide interfacing for 8 central office analog trunks.

The 8 telephone channels are brought out through 4 RJ45 connectors (8P8C telephone interfaces), with 2-channel multiplexing at each port: pins 4/5 for the first channel and pins 3/6 for the second channel. One standard network cable carries two voice channels, halving the cabling volume at the same subscriber line provisioning volume, and the use of patch panels and cable trunking decreases accordingly.

In urban areas, the desktop 8-channel multi-service optical multiplexer breaks through the limitations of twisted pair in terms of frequency band and transmission distance, expanding the service range of the switching office; in remote suburbs or at private network sites, cross-boundary line extension can be completed without building a new switching office, shortening the site enablement cycle accordingly.

Figure 1: Front appearance of the IDM-NT008 desktop 8-channel multi-service optical multiplexer, close-up of the 8 telephone indicator LEDs and 4 RJ45 telephone interfaces

What Functions and Interfaces Does the 8-Channel Multi-Service Optical Multiplexer Provide?

Function	Description
8 Telephone Channels	A single unit provides 8 telephone channels, supports FXO and FXS interfaces, and can connect 8 telephones or provide interfacing for 8 central office analog trunks
4 RJ45 Connectors for Telephone Interfaces	8P8C interfaces with 2-channel multiplexing per port: pins 4/5 for the first channel and pins 3/6 for the second channel; the 4 ports carry 8 telephone channels
8 Telephone Indicator LEDs	Solid on indicates the telephone channel is in use, flashing indicates ringing, and off indicates the channel is idle, displaying the real-time voice channel status of each channel
8/ALM Optical Fiber Alarm Indicator LED	Flashing indicates an optical fiber alarm and it stays off during normal operation, so the optical fiber link status can be judged on site
Optical Fiber Point-to-Point Access	Completes the connection between subscriber terminals or with the public switched telephone network through the optical fiber transmission medium, so calls do not depend on the public network
Cross-Boundary Line Extension	Replaces remote small offices and deferred switching offices, expanding the service range of the switching office
Desktop Installation with Compact Size	High integration and compact size, suitable for space-constrained locations such as equipment rooms, wiring closets and business outlets

The optical fiber access end is divided into TX and RX; TX connects to the RX at the opposite end, and RX connects to the TX at the opposite end. When the device at the opposite end is powered on and the optical fiber is properly connected, the 8/ALM indicator LED of the IDM-NT008 stays off; if the 8/ALM indicator LED flashes, it indicates a problem with the optical fiber.

Core Technical Specifications

Item	Parameter/Specification	Description/Applicable Conditions
Voice Interface	8 FXO/FXS channels	4 8P8C ports (RJ45 connectors) with 2-channel multiplexing per port (pins 4/5 for the first channel and pins 3/6 for the second channel)
Audio Range	300Hz～3400Hz	Meets the voice band requirements of the public telephone network
Compression	ITU G.711 A-law	64Kbps standard PCM voice codec, providing intercommunication with the public switched telephone network
Impedance	Three-element complex impedance 200Ω+560Ω//0.1μF	Meets the working conditions of standard analog telephone lines
Loop Current	25mA per channel	Feeding capability of each telephone interface
Optical Fiber Channel	1 point-to-point optical fiber channel	Single fiber transmission over 30~40km; the optical ports are divided into TX and RX
Optical Fiber Port	FC port by default	There are three interface types; special instructions are required at ordering according to the optical cable connector type
Transmission Distance	30~40km as the general configuration	Depends on the optical fiber type and link loss; it can be customized per project
Indicator LEDs	8 telephone indicator LEDs + 8/ALM alarm indicator LED	Solid on = in use / flashing = ringing / off = idle; a flashing alarm LED indicates an optical fiber alarm

Differentiated Value: Why 4 RJ45 Ports and Single-Fiber Long-Distance Transmission Save Cost

Differentiation Point	Capability and Value
8 Telephone Channels	A single unit provides 8 FXO/FXS telephone channels; one device completes subscriber line provisioning for 8 voice channels, reducing the rack positions and power supply requirements in the equipment room accordingly
Dual-Channel Multiplexing via RJ45 Connectors	The 4 RJ45 connectors carry 8 telephone channels with 2-channel multiplexing per port, halving the cabling; construction and maintenance involve only these 4 ports
30~40km Single Fiber	Single fiber transmission over 30~40km replaces remote small offices and deferred switching offices, so subscriber line provisioning does not require a new switching office
Optical Fiber Alarm LED	A flashing 8/ALM alarm LED immediately indicates an optical fiber link failure, so positioning requires no instruments and the troubleshooting time is shortened
Carrier-Class Voice Quality	G.711 A-law compression + 300~3400Hz audio; carrier-class voice quality with intercommunication with the public switched telephone network (PSTN)

How to Wire the Single-Fiber 8-Channel Telephone Optical Multiplexer

The telephone interfaces use 4 8P8C (RJ45) ports with 2 channels per port: pins 4/5 for the first channel and pins 3/6 for the second channel. The central office device connects to the SPC exchange and the device at the remote end connects to the telephone; check the service interface wiring sequence before powering on.

There are three interface types for the optical fiber ports; please specify according to the optical cable connector type at ordering. If no special instructions are given, the FC port is configured by default, and the transmission distance is generally configured for 30~40km. The optical fibers are connected in a crossover manner: TX connects to the RX at the opposite end and RX connects to the TX at the opposite end.

If there is no telephone service, troubleshoot in the following order:

• Check whether the central office and remote end devices are installed in reverse: the central office device connects to the SPC exchange and the device at the remote end connects to the telephone;
• Check whether the service interface wiring sequence is wrong: pins 4/5 for the first channel and pins 3/6 for the second channel;
• Check the optical fiber link; the 8/ALM indicator LEDs at both ends staying off means the optical fiber is normal;
• Check whether the telephone itself is intact.

Figure 2: Rear panel of the IDM-NT008 desktop 8-channel multi-service optical multiplexer, close-up of the FC optical fiber port and TX/RX ports

Typical Application Scenarios

Electric Power/Energy Private Network: 8 Telephone Channels at Remote Substations

In power/energy private networks, substations and switching stations have limited space in their communications cabinets, and the compact IDM-NT008 desktop 8-channel telephone optical multiplexer can be installed directly in the cabinet or placed on a desktop. On the substation side, only one optical fiber is needed to provide 8 telephone channels to the remote end, and the 4 RJ45 ports save cables and cabinet space, halving the cabling volume compared with conventional subscriber line provisioning. When the transmission distance is configured for 30~40km, the substation reaches the dispatch station directly over a single fiber, and dispatch telephones use a dedicated optical fiber channel throughout, independent of the public network.

Rail Transit and Tunnels Along the Line: 8 Section Telephone Channels Over a Single Fiber

Section telephones along rail transit lines and tunnels are numerous and widely spaced; the IDM-NT008 performs multiplexing of the 8 telephones in a tunnel onto one optical fiber, carrying 8 section telephone channels over a single fiber. The in-use and ringing status of the voice channels is visible intuitively through the panel indicator LEDs, so the duty operator can keep track of section telephone usage without going on site. Once the optical fiber becomes abnormal, the flashing 8/ALM alarm LED indicates the failure, and section telephones can be restored quickly with the TX/RX crossover wiring rule.

Mining Areas/Oilfield Field Operations Areas: Cross-Boundary Line Extension Replaces Small Offices

Mining areas and oilfield field operations areas are far from urban areas, and building a new switching office for a small number of telephones is not economical. The IDM-NT008 provides coverage for field operations areas with single-fiber transmission over 3040km, completing cross-boundary line extension for 8 telephone channels and replacing remote small offices and deferred switching offices, so both the initial construction investment and the later maintenance costs decrease. Voice uses ITU G.711 A-law encoding over an audio range of 300Hz3400Hz; the voice quality is clear, and the call experience between field operations area personnel and the dispatch center approaches that of a local telephone call.