IDM-NT202B Desktop 2-Channel Telephone Optical Multiplexer
Telephone and Ethernet convergence over the same fiber, dual ports with shared 100M and VLAN partitioning, saving a pair of devices
The IDM-NT202B desktop 2-channel multi-service optical multiplexer adopts a desktop-type chassis structure design and provides 2 telephone interfaces and 2 shared 100M Ethernet interfaces over one optical fiber channel. The Ethernet interfaces of the 2-channel telephone optical multiplexer can be partitioned into VLANs arbitrarily. The IDM-NT202B desktop 2-channel multi-service optical multiplexer can be widely used for public telephone network access and dedicated line information transmission in sectors such as telecommunications data services, electric power, banking, public security, military, schools, and expressways.
IDM-NT202B Desktop 2-Channel Telephone Optical Multiplexer is a 2-channel telephone and 2-channel Fast Ethernet optical multiplexer developed by Beijing Ruiguang Jiyuan Digital Technology Co., Ltd. (Raytrans). It adopts a desktop-type chassis structure and provides 2 telephone interfaces and 2 shared 100M Ethernet interfaces over a single optical fiber channel. It is used for public telephone network access and dedicated-line information transmission, and is a typical product showcase from an optical multiplexer manufacturer for small access scenarios.
The device extends voice and data services to each user area. It can replace remote small offices to perform cross-boundary line extension, and is also used for private network access by departments such as electric power, banking, public security, military, schools, and expressways. It is suitable for scenarios such as government private network optical fiber communication solutions and military emergency communications vehicle solutions. The desktop chassis measures 125 mm in length, 100 mm in depth, and 46 mm in height. It can be placed directly on a workbench in a wiring closet or on a small cabinet tray, without occupying a 19-inch rack position. As a compact 2-channel telephone optical multiplexer, its desktop structure facilitates flexible deployment; compared with multi-service optical multiplexers, this model focuses on a streamlined combination of two service types: telephone and Ethernet.
Key Specifications at a Glance: 2 telephone + 2 FE · shared 100M Ethernet · VLAN partitioning · sensitivity -36 dBm · 15 W low power consumption · desktop 125×100×46 mm · DC5 or AC 220 V dual power supply
What kind of device is the 2-channel telephone and 2-channel Fast Ethernet optical multiplexer
This device is a point-to-point optical fiber access device used in pairs at both ends. One end connects to the switching office side or central equipment room, and the other end is placed at a remote station. The two devices are connected by a single optical fiber, and voice and Ethernet services are transmitted bidirectionally over the optical path. All service ports appear in pairs on the same pair of chassis, so remote stations no longer need to configure separate transmission devices for telephone and network. As a typical product showcase model, it plays an entry-level role in Raytrans's 2-channel telephone optical multiplexer product line for converging voice and data over the same fiber.
The core of an optical multiplexer is to multiplex multiple services onto a single optical fiber: voice is encoded with ITU G.711 A-law and occupies fixed bandwidth, while Ethernet services are carried over a 100M channel. The two service types each occupy an independent channel over the optical path and do not contend with each other. G.711 is the voice codec standard specified in ITU-T recommendations. A-law is commonly used in domestic telephone networks, so telephones and switching equipment can interoperate directly without additional conversion equipment.
Figure 1: Front view of the IDM-NT202B desktop 2-channel telephone optical multiplexer with close-up of power and optical link indicator LEDs
The Ethernet side provides 2 shared 100M interfaces. The two ports share one 100M channel bandwidth and can be connected to the office network and video network separately by service, with VLAN partitioning on the device for isolation so that broadcast packets do not spread to each other. For remote stations with only one optical fiber in place, telephone and network are converged over the same fiber, eliminating another pair of optical multiplexers and the associated optical cable. For stations that need to carry voice, data, and video simultaneously, the multi-service optical multiplexer solution from the optical multiplexer manufacturer can also be compared during the selection stage, and the choice can be made according to the number of service ports and bandwidth requirements.
What services can one optical fiber carry
The service interfaces of the IDM-NT202B are configured in two categories: voice and Ethernet. The 2 telephone channels handle telephone or switching equipment access, and the 2 shared 100M Ethernet channels handle data services. All services share a single optical fiber channel. The functions and corresponding interfaces are listed in the table below for item-by-item verification against the site list; interface direction and ordering configuration are subject to the manufacturer's technical documentation.
| Function | Description |
|---|---|
| 2-channel telephone access | Audio range 300 Hz to 3400 Hz, ITU G.711 A-law compression, loop current 25 mA/channel, can connect to telephones or switching equipment |
| 2-channel shared 100M Ethernet | The two ports share one 100M channel, connecting to switches, acquisition terminals, or network cameras |
| VLAN partitioning | Ethernet ports can be partitioned into VLANs arbitrarily, different service network segments are isolated on the same channel, and broadcasts do not spread to each other |
| Single-fiber multi-service convergence | 2 telephone channels and 2 shared Fast Ethernet channels are multiplexed onto one optical fiber, replacing two single-function devices and one optical cable |
| Integrated multi-function design | Voice, Ethernet, optical transmission, and power supply are integrated into a desktop chassis, and only service cables and optical patch cords are connected on site |
| Optional optical interface | FC optical port by default; SC and other types can be customized according to the on-site optical cable termination method; single-mode is the standard configuration |
| Dual power supply mode | DC5 or AC 220 V power supply modes are available, so both equipment rooms and DC sites can draw power directly |
| Alarm indication | The panel provides power, optical link, and service status indications; when the link is abnormal, the fault section can be determined by the indicator LEDs |
What distinguishes the function table most directly from an ordinary telephone optical multiplexer is the two Ethernet channels: voice and data are carried independently, so an abnormality in one service does not affect the other. The remote end simply connects cables by service port, without additional configuration to manage voice and data on one device at the same time. If a site has more service types, the expansion capability of multi-service optical multiplexers can be further explored and configured as needed.
How does shared 100M Ethernet partition VLANs
The 2 Ethernet ports share one 100M channel inside the device, and VLANs are partitioned on the service ports: office, video, and acquisition services are each assigned to a VLAN, ports are tagged according to their VLAN, and data still shares the same 100M bandwidth over the optical path. In this way, a remote end needs only one pair of devices to make data of different departments invisible to each other, without laying separate optical fibers for each department.
Before partitioning, list the correspondence between network segments and ports clearly according to the service list, and then write consistent VLAN configurations on the devices at both ends. Inconsistency between the two ends will cause the link to appear normal while cross-network-segment communication fails. Bandwidth is calculated as shared 100M, and when both ports are at full load simultaneously, bandwidth is allocated according to total bandwidth. For video and acquisition services, time-sharing or rate limiting is recommended to avoid saturating the channel and affecting other data services. In government private network optical fiber communication solutions, this VLAN isolation approach is often used to distinguish office and service network segments on the same optical path.
Key specifications: how to verify optical interface, telephone, Ethernet, and power supply
The specifications are listed in five groups: optical interface, telephone interface, Ethernet, power supply and power consumption, and environment and structure. The devices at both ends are used in pairs, and the wavelength and interface type of the optical interfaces must match. The verification order is to first check whether the link loss falls within the optical power budget, then confirm the number of voice channels and Ethernet ports, and finally verify the power supply mode and installation space.
Optical interface parameters
| Item | Parameter/Specification | Description/Applicable Conditions |
|---|---|---|
| Interface type | FC (SC and others customizable) | Selected according to the on-site optical cable termination method |
| Fiber mode | Single-mode (multi-mode optional) | Single-mode is the standard configuration; multi-mode is confirmed per project |
| Optical channel | 1 channel | Used in pairs at both ends, with receive/transmit directions connected correspondingly |
| Optical fiber rate | 155 bps±50 ppm | As stated in the original product documentation; the optical port rate is subject to the manufacturer's technical documentation |
| Wavelength | 1310 nm | The wavelength and interface type at both ends must be consistent |
| Transmit optical power | -2 to -11 dBm | Available optical power range at the transmit side |
| Receiver sensitivity | Better than -36 dBm | Lower limit of available optical power at the receive side; usable for weak optical links |
Telephone interface parameters
| Item | Parameter/Specification | Description/Applicable Conditions |
|---|---|---|
| Number of telephone channels | 2 channels | Can connect to telephones or switching equipment |
| Audio range | 300 Hz to 3400 Hz | Telephone voice bandwidth |
| Impedance | Three-element complex impedance 200 Ω+560 Ω//0.1 μF | Matched to SPC exchanges and ordinary telephone side |
| Compression | ITU G.711 A-law | Common codec in domestic telephone networks, interoperable with mainstream switching equipment |
| Loop current | 25 mA/channel | Ensures normal power feeding to telephones |
Ethernet, power supply, and environment parameters
| Item | Parameter/Specification | Description/Applicable Conditions |
|---|---|---|
| Ethernet interface | 2 shared 100M | The two ports share one 100M channel; VLANs can be partitioned on the ports |
| Ethernet service | Data access and dedicated-line transmission | Connects to switches, acquisition terminals, or network cameras |
| Power supply mode | DC5 or AC 220 V | AC is drawn in mains-powered wiring closets, DC is drawn at DC sites; selected at ordering |
| Overall power consumption | 15 W | Lower power draw and heat dissipation pressure for long-term online operation |
| Operating temperature | 0℃ to +50℃ | Equipment room, wiring closet, and well-ventilated equipment box environments |
| Relative humidity | 95% non-condensing | Applicable condition for high-humidity environments is non-condensing |
| Dimensions | 125×100×46 (mm, Length×Depth×Height) | Desktop structure; can be placed on a desktop, in a wall-mounted box, or on a small cabinet tray |
For the two optical interface items, verify the interface type first and then the optical power: FC is the default, and when the optical cable termination is SC or another type, specify it at ordering to avoid adding fiber adapters on site. Single-mode 1310 nm is the standard configuration, and multi-mode is confirmed per project. Services can be enabled only when the wavelength and interface type of the devices at both ends are consistent. In scenarios such as military emergency communications vehicle solutions that require rapid deployment and variable link conditions, advance verification of the optical interface type and optical power budget is particularly critical.
Differentiated value: single-fiber convergence, -36 dBm sensitivity, and 15 W power consumption
Each of the three differentiated capabilities has verifiable specifications that can be copied directly into technical specifications and bid parameter tables during the design stage. All three hold simultaneously in private networks such as electric power, public security, military, and expressways, where sites are distributed and equipment room conditions vary, and they are also the main differences between this device and ordinary telephone optical multiplexers that carry voice only.
| Differentiation Point | Corresponding Capability and Specifications | Applicable Conditions and Value |
|---|---|---|
| 2 telephone + 2 FE single-fiber convergence | 2 telephone channels and 2 shared 100M Ethernet channels are multiplexed onto one optical fiber; Ethernet ports can be partitioned into VLANs arbitrarily | A remote station with one fiber in place can enable voice and data simultaneously, saving a pair of optical multiplexers and one optical cable |
| Sensitivity -36 dBm | Transmit optical power -2 to -11 dBm, receiver sensitivity better than -36 dBm, 1310 nm single-mode | Weak optical links with higher optical cable loss and more splice points still have power margin, and voice and data continue to be transmitted |
| 15 W low power consumption | DC5 or AC 220 V dual power supply, overall power consumption 15 W | Both mains-powered wiring closets and DC sites can draw power directly; unattended equipment rooms do not need power supply or heat dissipation upgrades |
| Desktop 125×100×46 mm | Desktop-type structure, high integration | Can be placed on a workbench, in a wall-mounted box, or on a small cabinet tray without occupying a rack position |
The practical significance of sensitivity better than -36 dBm lies in legacy optical fiber private networks: when received optical power drops to a low level close to the threshold, the device can still demodulate voice and data signals. Such links commonly suffer from aging splice points, dust on fiber adapter end faces, and insufficient optical cable bend radius, and it is exactly this receiver sensitivity margin that supports continued service over the existing optical cable. As an optical multiplexer manufacturer, Raytrans retains this sensitivity margin in this product series, facilitating rapid deployment of government private network optical fiber communication solutions and military emergency communications vehicle solutions over existing optical cable resources.
How to calculate weak-light long-distance links
Whether a link can be enabled is calculated using the margin between transmit optical power and receiver sensitivity: the IDM-NT202B has transmit optical power of -2 to -11 dBm and receiver sensitivity better than -36 dBm. Calculated at the lower transmit limit of -11 dBm, the available link loss is about 25 dB; calculated at -2 dBm, it is about 34 dB.
The calculation order is to first measure the actual route length, accumulate splice point and fiber adapter losses according to the per-kilometer optical cable loss, and then compare with the available budget of 25 to 34 dB, leaving about 3 dB spare at each end in engineering practice. If the budget is insufficient, first clean the optical fiber end faces and reduce fiber adapters; if still insufficient, consider replacing optical modules or using segmented repeaters. It is not recommended to use the full theoretical distance.
Typical application scenarios
Electric power private network: dispatch telephone and data backhaul over the same fiber for substations and power supply stations
Substations, switching stations, and power supply stations are distributed across urban and suburban areas, with inter-station distances ranging from a few kilometers to tens of kilometers, and most equipment rooms have no permanent on-duty personnel. This telephone optical multiplexer, the IDM-NT202B, uses one optical fiber to deliver 2 dispatch telephone channels and 2 shared 100M Ethernet channels to the remote end. Dispatch calls and in-station meter and status data are backhauled over the same link, eliminating the need to lay separate cables for the two service types.
Power supply access conditions vary at electric power sites: urban wiring closets mostly have AC mains power, while suburban and field sites may have only DC power. The device supports two power supply modes, DC5 and AC 220 V, with overall power consumption of 15 W. Sites can draw power according to existing power supply conditions, with no need to add a dedicated power distribution panel or fan for this device.
Public Security and Military Private Networks: Independent Voice Channels Between Duty Posts and Command Posts
Duty posts, checkpoints and temporary command posts are often far from switching offices, and public network telephony is usually not suitable as the sole communication means. The IDM-NT202B 2-channel telephone optical multiplexer extends 2 telephone channels to duty posts, with all calls carried over dedicated optical fiber channels and physically isolated from the public network; the 2-channel shared 100M Ethernet is used for duty terminals and video backhaul, with voice and data on independent channels that do not contend with each other.
Equipment room conditions at field duty posts are simple. The device is compact with clear wiring relationships, and services can be enabled by connecting optical fiber patch cords and telephone lines according to the labels. When a link is abnormal, first check the panel alarm indication, then measure the received optical power with an optical power meter and compare it with the sensitivity specification of better than -36 dBm to determine whether the cause is equipment failure or excessive optical cable loss.
Expressway Electromechanical Systems: Service Extension to Toll Stations and Monitoring Points
Toll stations, service areas and monitoring points along an expressway are distributed along the line, with spacing between stations ranging from a few hundred meters to more than ten kilometers. The electromechanical system simultaneously runs toll telephones, monitoring and the office network. The IDM-NT202B, in a desktop enclosure, is installed in a small cabinet or wall-mounted box in the toll station equipment room, and a single optical fiber delivers 2 telephone channels and 2-channel shared 100M Ethernet to nearby sites, so duty calls do not depend on wireless coverage.
The data service of the electromechanical system needs to be separated from the office network. The 2 Ethernet ports support VLAN partitioning, so toll data, monitoring data and office network segments are isolated from each other on the same channel. Cabinets along the line are mostly unattended. The device is installed in a well-ventilated cabinet under temperature and humidity conditions of 0℃ to +50℃ and 95% non-condensing, and can then operate online over the long term.
How to Deploy On-Site Wiring and Service Activation
Wiring corresponds to service types item by item: telephones use telephone lines, Ethernet uses network cables, and optical paths use optical fiber patch cords. Devices at both ends are configured as a pair, with service ports corresponding one to one. Before installation, verify the number of interfaces and the VLAN configuration at both ends, then enable services item by item in the order below, so that if all services are enabled at once you can still tell which segment a point of failure lies in.
| Service | Equipment-Side Interface | On-Site Connection | Description |
|---|---|---|---|
| Telephone | Telephone interface | Telephone, switching equipment | Audio range 300 Hz to 3400 Hz, A-law per ITU G.711 |
| Ethernet | 2-channel shared 100M | Switch, acquisition terminal | The two ports share one 100M channel, partitioned by VLAN |
| Optical path | FC (SC and others can be customized) | Optical fiber patch cord, optical cable | Single-mode 1310 nm; wavelength and interface type paired at both ends |
| Power | DC5 or AC 220 V | Mains power or DC power | Select one of the two according to on-site power supply conditions |
- Power-on self-test: connect DC5 or AC 220 V power, confirm the panel power indication is normal and there is no obvious temperature rise on the unit; overall power consumption is about 15 W.
- Optical path verification: clean the fiber end face, connect the patch cords, and measure the received optical power with an optical power meter to confirm it is above the sensitivity threshold of better than -36 dBm.
- Telephone activation: connect telephones or switching equipment, go off-hook on each channel and listen to confirm ringing, conversation and hang-up release are normal.
- Ethernet activation: connect switches and terminals, confirm the two ports communicate normally, then complete VLAN partitioning by service network segment and verify consistency at both ends.
- Record and archive: register the device numbers at both ends, the received optical power at the optical ports, and the correspondence between service ports and VLANs as a comparison basis for subsequent inspection.
How to Select a 2-Channel Telephone 2-Channel Fast Ethernet Optical Multiplexer
Selection proceeds through five items: service list, Ethernet requirements, optical interface, link budget, and power supply and installation position. The IDM-NT202B is a desktop 2-channel telephone optical multiplexer with a shared 100M Ethernet channel. All five items correspond to conditions verifiable on site, so the configuration can be determined by confirming them one by one during the design stage, without waiting until after ordering to change interface direction and power supply type.
- Service list: confirm that the remote end needs 2 telephone channels and 1 to 2 Ethernet services; if more channels or sites are needed, add paired devices per site rather than stacking capacity on one device.
- Ethernet requirements: confirm whether data services need to be isolated on the same channel; if so, include the VLAN scheme and network segment partitioning in the design document.
- Optical interface: confirm the optical cable termination method (FC or SC, etc.) and fiber mode; single-mode is the standard configuration, and multi-mode is confirmed per project.
- Link budget: calculate according to the actual route length and the number of splice points and fiber adapters; estimate the available budget at 25 to 34 dB, and if insufficient, first optimize end faces and adapters.
- Power supply and installation: use AC 220 V where mains power is available in the wiring closet, and DC5 where only DC power is available on site; the desktop enclosure measures 125×100×46 mm, so confirm the placement position and heat dissipation clearance according to on-site space.
