RF over Fiber Guides | ViaLite Communications

Laser Options

A number of choices are available for lasers in ViaLite products. The standard DFB laser provides excellent performance for most applications. However high power and dual isolated lasers are available for high performance applications. Also, WDM and CWDM lasers are available for applications where up to 18 channels are multiplexed down a single fiber. Distributed feedback (DFB) lasers: ViaLiteHD fiber optic links use distributed feedback (DFB) lasers. Dual isolated… Read more »

The Cost of Ownership of RF over Fiber

Although product pricing can often be the deciding factor when purchasing goods, the Total Cost of Ownership (TCO) is often overlooked. However this is an important factor, which should be considered. The cost of ownership of RF over fiber products varies greatly by manufacturer. ViaLite Communications is one of the few to address TCO at the time of designing and manufacturing its RF over fiber links. ViaLite addresses the following three areas… Read more »

Powering Customer Equipment

On-board LNB/LNA powering – option 4 This option is only available on rack chassis cards. The on-board powering function is only available on transmitters (single, dual or transceiver). Voltages are fed through the Tx RF input connector from within the RF over fiber card and can be used to power connected equipment, typically an LNA or LNB. This solution is an internally generated +13/18V selectable LNB/LNA voltage, with 22 kHz... Read more »

Setting Gain

ViaLiteHD chassis cards are factory set and ready to operate with a default gain setting. This gain is selected by the customer at the time of order. Each card has a margin of gain and attenuation which sits either side of the default setting. This window is typically 15 dB wide and can be adjusted by soft gain control (SGC), manual gain control (MGC) or automatic gain control (AGC). It is possible to adjust the gain settings in both the transmitter and the receiver… Read more »

ViaLite Horizons SNMP GUI showing a 3U chassis

APC vs PC Connectors

Fiber connectors are not all the same. As well as the different physical types – such as SC, FC and E2000 – there is a big difference between APC and PC or UPC connectors. This difference is especially important when sending RF signal (as opposed to digital data). What is the difference? PC and UPC are flat connectors with a straight polished fiber. ‘APC’ is an angled polished connector; the fiber is... Read more »

Install and Setup a Fiber Link

In 10 steps… 1. Remove dust covers from your cross site fiber (or patch leads) and the connectors on the RF over fiber links. 2. Clean the cross-site cable; dirty fibers cause performance issues. a) Peel the plastic cover from an unused “N” cleaning pad. b) Hold the connector between your thumb and forefinger. Clean the connector using firm pressure by swiping in a pendulum motion through each segment of the “N” shape… Read more »

One of the new ViaLiteHD 3U Chassis installed at BT's International Communications Centre in Madley

The Benefits of Blind Mate

Adding blind mate to RF over fiber links allows for simple and fast “hot-swapping” of links and minimizes downtime. The benefits of blind mate include: The hot-swapping of a card can be carried out in seconds – dramatically reducing downtime and providing five nines (99.999%) reliability; There is no risk of disturbing other on air connections when adding, removing or changing services; Simple plug and play to add services; The re-configuration of a rack chassis can be carried out quickly… Read more »

ViaLite blind mate rf over fiber shown on 3U rack chassis

Electro-Optical Conversion Process

Optical Transmitter. At the heart of the module that converts RF signals to light is a laser diode. The basic principle is direct modulation of the incoming RF signal onto the output of the laser diode. An example of the intensity output from a typical laser diode is shown in Figure 1. The RF input signal directly modulates the laser diode bias current about the optimal DC working point, sometimes referred to as the quiescent point, which is typically 40mA… Read more »

Figure 1: Graph showing laser diode analogue response

Optical Connector Options

ViaLite recommend the use of angled (APC) connectors because these minimize reflections at the fiber-air interface. Angled (APC) and standard (PC) connectors must not be confused. The two connector-types are not interchangeable and mating one with the other will damage both the cable and the module connectors. SC/APC is the standard connector recommended for ViaLite links. Alternative connector options available when ordering ViaLite equipment are FC/APC, E2000/APC and LC/APC… Read more »

SC/APC connector option. SC/PC cannot be used

Blind Mate Connectivity

Based on 50Ω SMA or 75ohm BNC (electrical) and LC/APC (optical) connectors, blind mate connectivity supports simpler and faster hot-swapping and minimizes down time. Hot swapping: Adaptors are fitted to the rear of a ViaLiteHD chassis to accept RF cards with blind mate connectivity. Electrical and optical connections are made to the rear of the chassis rather than directly to the card. This means that cards can be easily removed and… Read more »