RF over Fiber FAQs

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What is the correct optical connector?

We recommend the use of FC/APC connectors to minimise back reflection of light into the laser, however ViaLiteHD supports a range of optical connectors.  These vary depending on the product type.  Please check the datasheet for each product.  Typical connectors are FC/PC, LC/PC, SC/PC, E2000/APC, FC/APC, LC/APC, and LC/APC


How are connectors cleaned?

Information on how to clean the connectors can be found on pages 12-13 of the RF Link Handbook.


How are the PSUs powered?

Each PSU requires a mains connection; for two PSUs there must be two mains connections.


Are the PSUs working?

The LED on each PSU will be lit green.


How to confirm a Tx card is working?

  • The power LED will be lit green.
  • The alarm LED will be lit green (this means the laser is enabled).
  • Is the optical transmit power correct? 3 mW = 4.5 dBm.
  • To measure optical transmit power an optical power meter and patch lead is needed.


How can I check the Rx card is working?

  • The power LED will be lit green.
  • The alarm LED will be green (this means the light load received is sufficient to operate).


I have a valid signal but the receiver module still has a red LED on?

It is very easy for a fiber-end to become contaminated with dirt. All ViaLite equipment is supplied with a cleaning kit. It is recommended that a fiber-end is cleaned before inserting into the connector. When using FC/APC connectors, please note that these have a single slot ‘key’ position that must be mated first before the thread is tightened. Please see the Fiber Optic Cleaning Kit guidelines for full details: Fiber Optic Connector Cleaning Guide (72793-HB-5) – for 72793 kit (standard cleaning kit) – Updated version 06/04/21 (June 4).



Do I need to upgrade the software in my current ViaLiteHD SNMP card to run Horizons?

ViaLite Horizons should be used with the latest firmware file.


 How do I perform a HRC-3 software update?

Instructions can be found in this guide: Performing a HRC-3 software update.



Is it possible to have multiple carriers having quite different powers beyond a module single range?

The out-of-band performance of the fiber optics links is not specified. Typically, a ViaLite L-Band HTS module will have some response from, say, 400 MHz to 2.5 GHz and no filtering is included to limit this. It is suggested that if you have out of band signals which might compromise the IP3 of your link then the addition of a filter or diplexer would improve performance.


What type of optical connectors can I use with ViaLite RF over fiber systems?

Optical connectors are critical to the performance of a link. We recommend the use of FC/APC connectors to minimize back reflection of light into the laser. Huber and Suhner part number FCPC-Z/M-A601 are FC/APC narrow key connectors offering >60 dB return loss. However, ViaLiteHD supports a range of optical connectors. These vary depending on the product type. Please check the datasheet for each product.


What are the limitations on the test ports?

BNC test ports can be found on the front panel of ViaLiteHD rack chassis cards. 50 Ohm test ports provide a test signal 20 dB less than the traffic signal. For 75 Ohm test ports the test signal is 14 dB less than the traffic signal on receivers and 26 dB on transmitters.


What is the limitation of the RF detector on GUI?

P1dB to -30.


What different options are there for output pin voltage on OEM modules?

Option 0 = 0v. Option 1 = 5v. Option 2 = 12v. Option 3 = supply via rear connector.



Why is gain lower for L-Band HTS cards?

L-Band HTS links use wider bandwidth gain stages. It is therefore not possible to have the same gain.


Why is gain different on 75 Ohm cards than on 50 Ohm cards?

The cards are built as 50 ohms, we then use a resistive transformer (minimum loss pad) to convert to 75 ohm, which loses 6 dB.


Dynamic Range

Why is ViaLite’s dynamic range so large?

We use active biasing & high quality lasers to achieve a very large dynamic range.


What is benefit of a large dynamic range?

Easy setup, good CNR (carrier-to-noise ratio) and good CIR (carrier-to-interference-ratio).


What is the difference between dynamic range (DR) and spurious free dynamic range (SFDR)?

SFDR is independent of application bandwidth.



What is the LNB maximum current per channel?

Single channel = 700 mA. Dual channel = 350 mA.


Why is the LNB/LNA voltage the same for both channels on a dual card?

There is only room for one circuit on the current design.


If an LNB noise figure is <1 dB and an SSPA is 8 dB; how come ViaLite’s noise is good when it is 20 dB and why is it not important?

This is because there is either (i) gain ahead of the link or (ii) the original signal is relatively high power (Flic’s law).



How will Brexit impact on our relationship?

ViaLite successfully sells and trades across most continents across the globe, including of course the European Union (EU). At a political level there is much discussion about what format the UK leaving the EU (“Brexit”) will take, but we are confident that ViaLite’s business and existing processes are well prepared for this.

If the UK Government agrees a withdrawal deal from the EU, for the near term nothing will likely change as we enter a transition period where free trade continues uninterrupted. If the UK Government is unable to make a withdrawal agreement with the EU – and we fall-back to World Trade Organization (WTO) trade terms – then the impact on ViaLite type products is likely to be low.

ViaLite RF over fiber products are typically described as “Transmission apparatus for radio-broadcasting or television, incorporating reception apparatus,” and this product classification is typically zero rated for import duties within WTO trading countries. VAT should be unaffected by Brexit.

The final consideration is the material used in ViaLite‘s product manufacture. Some of our most expensive precision parts are actually purchased from the Far East and Japan, so non-EU countries unaffected by Brexit. We do have some components sourced from the EU via UK distributors and we will work with them to ensure disruption is minimized.


RF over Fiber FAQs
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