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FAQ
- Which kind of redundancy is guaranteed from Optocore?
The Optocore network offers three different aspects of redundancy.
Fibre structure. Connecting the first device with a pair of fibres to the next and doing the same up to the last
device, you enable the first ring, which is enough to run the system. To enable the redundant ring, it is
sufficient to close the loop connecting, by means of an additional pair of fibres, the last device to the
first one. Once the redundant loop is enabled, any connection can be lost (fibre disconnection or break)
without effecting the integrity of the network. In a matter of one sample time, the system will switch-over
the redundant connection, without interruption of the data flow. As soon as the previously disconnected fibre
will be available again, it can be reconnected "on-air", with no need of network reboot or re-configuration by
the user.
Power supplies. Every Optocore network device is equipped with dual redundant power supply, completely
independent, with different power cables and protection fuses. The automatic switch-over guarantees the
continuity of the power supply of the unit in case of PSU failure. All the Optocore power supplies are
400V tolerant; in case of over voltage a protection occurs, indicated by means of a specific LED in the
front panel.
Work Clock Recovery. In a digital synchronous network, one device is determined as Word Clock Master,
all the other are slaves and accept the Word Clock distributed by the master. In case of failure of the Master
device the complete network would be unlocked and unusable. This is not happening with the Optocore network
because, if this problem occurs, the system reacts in a matter of one sample time, determining another working
device as new Word Clock Master, recovering, with no interruption, the complete network functionality. In the
very unlikely case of a double fibre disconnection, the former ring will be divided in two different networks,
but, at least, the two independent rings will have a Word Clock Master each, working separately. As soon as
one of the connection will be re-established, the system is recovering the work clock distribution, determining
a single device as Master Word Clock, for the entire network. This Word Clock Management is automatically
determined, not a single action is required by the user. The devices having the lowest ID in the network is
the Word Clock Master. It is possible to force a specific device to be the master even if it has not the
lowest ID, by selecting a Master Clock priority flag in the local setting. In case of multiple devices
with priority flag set, the selection of the master will be done before between those devices, then between
the others, selecting the one with the lowest ID.
- For professional applications, should I use an external Word Clock Generator?
The Optocore network runs at 1Gbit/sec. Therefore the system word clock is 1Gbit and of a very high quality,
extremely low jitter, to guarantee the synchronous and error free transmission. When the sample frequency
of the audio is selected at the typical values of 48 (or 96) kHz, the clock for the internal A/D and D/A
converters and for all the external devices is produced by a division of the 1Gbit system clock and distributed
at any node. For this reason the quality of the word clock offered by the Optocore system is of the highest,
since the already negligible jitter of the 1 Gbit clock is extremely reduced by this operation, when it is
divided down to a 48 (or 96) kHz. For this reason, the Optocore Network should be preferred as word clock
master, although it is possible to accept external word clock sources, via dedicated devices.
- Optocore is a synchronous network, which are the advantages?
Audio & video are synchronous signals, therefore the best way to transport it is via a synchronous network.
The data and the clock are running together and all the devices connected to the network
(Optocore and non Optocore) work with the same clock.
One of the biggest advantage of this style is the extremely low latency of the network. From any input to
any output (digital to digital) that amount is only 41uS. This is a fixed figure, not dependant from the
signals path, the number of the channels used, the length of the fibres and includes the time necessary for
a complete matrix.
Thanks to this design, the Word Clock is available at any node, from devices equipped with digital In&Out.
The theoretically advantages of the Asynchronous transmission (i.e. the re-transmission of lost data packages)
are useless in real time situation, such the Live applications. You cannot stop the
time and "The Show must go on!"
- Which kind of network topology can use with Optocore? Star? Ring? Mixed?
All the Optocore network devices are always connected in a ring.
The ring structure offers multiple advantages. Once a signal is accepted in the network
from any point, it is available for output there and at any other point, with no bottle-neck
in the data availability. Closing the loop of the fibres from the last to the first device
(establishing the second ring) this structure offers the complete redundancy with the smallest
fibre count, very important for mobile application. Example: N devices connected in a redundant
ring require N fibres. The same amount of devices (N) connected in a redundant star network
topology, would require 2N-2 fibres, almost the double.
All the devices in the ring have the same importance and do not require a central unit (or main Hub),
sharing the complete protocol. In the unlikely event of a faulty unit, the rest of the network will
remain fully working. This is not guaranteed in the star networks, where the central device is crucial.
The malfunction of that device would breakdown the entire system.
- Is Optocore using a standard fiber protocol? Which kind of data can be transported? How many channels?
The protocol used by Optocore is proprietary. The 1 Gbit bandwidth allows the transmission of
512 audio channels with sample frequency of 48 kHz (256 @ 96 kHz) by means of a single fibre
optic cable. That bandwidth can be shared and utilized for the transmission of other signals
as well, such as video and data. The Dynamic Input Allocation allows the user to customize
the kind and the number of signals of its network, always respecting the limit of the bandwidth. It's
important to underline that only the number of the inputs does matter for this calculation.
Outputs do not use "space on the fibre" and once a signal is present in the network, it can
be routed as output, as many time as the user wants. The stage device LX4AP, i.e., which is
equipped with 48 Mic level Inputs and 16 Line level outputs, is using only 48 channels of
the protocol (of the 512 available) and not 64, as one may think.
- Is it possible to transport Ethernet as well?
Yes, by means of DD6NEs. They have each 6 standard RJ45 ports and use part of the OPTOCORE network for
Ethernet, and all devices create automatically a big switch - as if all devices connected were in
the same room in the same network, even when they are really hundreds or thousands of meters away.
In addition the devices extend your LAN far beyond the technical limits of a traditional Ethernet.
The devices feature fully IEEE 802 compatible 10/100Mbit Ethernet ports, but enhance it by redundant
power supplies and a guaranteed fibre redundancy without difficult Ethernet setups like spanning tree.
Don't get confused: Optocore IS NOT USING Ethernet for the audio distribution, but allows
the "tunnelling" of it via the fast, synchronous, redundant fibre optical network, together
with all the other data.
- Which are the best optical connectors for fixed and mobile applications?
The optical interfaces of the SC-type, equipping all the Optocore network devices, are absolutely reliable
for fixed installations and indoor use.
The lighting data exchange is guaranteed by the mechanical alignment of the connectors, as reported in the
image below.
For more rugged applications e.g. mobile usage, expanded beam connectors mounted on 1U panels are available,
along with matching, inter-connection cables transported on cable drums.
The expanded beam technology ensures maximum safety in optical data exchange, by coupling beam expander
& beam focusing lenses to enlarge the contact surfaces. This method is perfect for digital transmission
where the optical budget loss of this kind of connectors is not critical and very well compensated
by the highest reliability of the light's communication. Dust or moisture cannot interrupt completely
the light flow between Optocon connectors. They can also easily be cleaned on the road.
Since the plugs of OptoCons are of the hermaphroditic type, a drum cable can be extended by simply
connecting the next one, without any additional plugs coupler.
- Why has OPTOCORE just a maximum of +18dBu input level, as +24dBu are generally preferred for long
distance cables?
Because OPTOCORE utilizes a digital transmission method, completely different from the analog style.
This means that even for long distances there is no signal loss and due to the interference free
behavior of the fiber the signal arrives to the destination point undistorted, clean and with the
same level of the origin. Since with 18dBu any analog input (Power amplifiers, Analog consoles,
Recorders, PA management systems, ...) can be fully driven, there is no reason to accept higher
signals in input.
- Do I need special extension plugs to connect more than one optical cable drum?
No, the OPTOCORE military connectors are hermaphroditic, this means that you can connect a
plug directly to the next one.
- Is the quality of the sound depending on the number of the channels you are using?
No, not at all. The protocol that OPTOCORE transports is fixed and transmitted entirely. The amount of data will
not change with the real amount of audio channels connected in input or output.
- Can I use my traditional intercom system via OPTOCORE?
Not straight. You cannot send voltage by fibre. But you can use a couple of analog channels to
have a full duplex communication.
- Does the system depend of the external computer and Windows OS?
No, the external software is just a big remote control. If you disconnect the computer when the system
is running, you simply let it work with the latest configuration you have set.
- Can you use analog and digital consoles at the same time, in the same network?
Yes, you can have up to 8 different network devices in the same ring. All of them can be DD32
(digital interface) of LX4A/B (analog in-out).
- Which is the system latency? Is that fix or depending on the amount of data in the network?
The intrinsic signal delay of an OPTOCORE channel through the fibre is extremely small and is dominated
by the necessary converting times. All data streams transmitted through similar channel types will
appear at all outputs on a network at the same time. Transmission delay is negligible amounting to
less than 200ns for each unit attached to the network. Beside the delay caused by the finite light-speed on a fiber,
which must be taken in account with very long distance transmission, there is no notable summing of
delay throughout the units in a OPTOCORE network.
The processing of AD converted audio signals causes typically a delay of 39/FS and the processing of
DA converted audio signals causes typically a delay of 28/FS (FS = sample frequency).
For synchronisation purposes and data re-arrangement another maximum of 2/FS needs to be calculated.
The result is a delay of only 69/FS from “analog to digital to light to digital and back to analog”,
which calculates to a maximum of 1.44ms @ FS=48kHz and 0.72ms @ FS=96kHz. Thus the processing of
already converted audio signals as with the DD32, causes the above mentioned maximum delay of 2/FS,
which calculates to a maximum of 42µs @ FS=48kHz and 21µs @ FS=96kHz.
- Can I install the external software on my Mac?
There is no software control for Mac OS, but we tested the OPTOCORE Windows software with Virtual PC
(for MAC) and it runs perfectly.
- Is the level of the OPTOCORE microphone pre-amplifier direct controllable and recallable from my Yamaha Digital
console? What about other brands console?
This is possible from Yamaha console via the Yamaha Emulation Mode of the optocore devices.
It emulates the presence of Yamaha AD824's or AD8HR's to let you control the gain and phantom
via the Remote port of the Yamaha console. This remote signal is transmitted by means of a couple
of RS485 ports of the DD32 device.
Di.Gi.Co. consoles can fully control OPTOCORE devices directly.
For all other brand there is no direct control, even if the OPTOCORE serial control protocol is available
for the manufacturers who wants to implement that in their consoles/devices.
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