Components

• Designed for networking NEXUS Base Devices using standard duplex fibre-optic cables
• 1…4 ports, application-specific configuration (can be changed at any time)
• 256 audio channels plus control and sync information per port
• No additional cabling required for control and synchronisation
• Extensive error recognition
• Supports redundant lines (changeover within one audio sample)

The Router Fibre-Optic Connection board provides interconnectivity between NEXUS STAR routers and to the NEXUS system using conventional duplex fibre-optic cables.

The board allows for four independent duplex connections transferring all audio and control data required for audio network operation; extra cabling is not required.
The ports available on the board are largely independent.

Fibre-Optical Connection

Using fibre-optic connections allows high data rates up to 1.25 Gbps and distances of up to 100 kilometers between two Base Devices. Highly distributed audio networks are thus possible.
Depending on the mode used each fibre-optic connection can transmit 256 or 512 audio channels for each cable and direction plus control and sync data. Thus the board is usable for a wide range of applications.

Transmission Capacities

The available transmission rate of 1.25 Gbps will allow data streams to be combined in the future. This means that a single fibre will be capable of handling 512 channels, which corresponds to the overall data capacity of two Base Devices. Above all, this clustering feature will significantly reduce installation costs, in particular, when spanning great distances.

Capacity per Port

Two different operating modes are available for RFOC ports to achieve an optimum utilization of the I/O resources:

256-channel Mode

• 256 I/O channels per port

512-channel Mode

• Clustering of 2 ports (max.) with 512 channels (2 × 256) each
• Supports communication to two Base Devices with 256 channels each

The capacity allocation is not limited in its geographical or time sequence.

Audio Channels

The audio channels are transferred with the full 30-bit resolution in an uncompressed format. This allows for complete and transparent AES/EBU-signal exchange between two Base Devices.

Control Data

The control data is transmitted in the form of a buffered transparent transmission channel asynchronous to audio and sync data. The maximum net data rate depends on factors such as the system clock, the operating mode, and the protocol used.
Control data is mainly used for communication between Base Devices (system control) but may also be utilized for distributing ancillary data on the NEXUS network.

Sync Information

Sync data includes the internal word clock of the transmitting Base Device. A Base Device can be synchronized to any fibre-optic connection and makes its internally synced wordclock available at the wordclock outputs of the RCX and XCPU controller boards. Therefore, one Base Device can act as a master device on the NEXUS network, and all other Base Devices will synchronize to it via their fibre-optic lines. There is no need for an extra wordclock connection between Base Devices.

Compatibility and Reliability

The protocol used by the RFOC board is compatible with the one used by the NEXUS XFOC07 board. The data streams from and to the respective ports are subdivided into blocks and are marked with a signature to be verified by the receiver. In case of error, this allows the respective ports to be muted automatically after a timeout.
The communication-data pre-processing is performed using an extra signal processor monitored by a watchdog.
The largely independent nature of the ports provides for high resilience against hardware errors in redundant operation via the same board. Data loss during the changeover is prevented as the current audio sample is always memorized.

Options

On request, the following optical-transceiver options are available:

• For variable wavelengths
• For spanning distances of up to 100 km (>62 miles)
• With duplex modules (both transmission directions on a single fibre)