32 channel Fibre Lite video receiver

Here we have it a Fibre Lite card cage populated sixteen 2 channel video receiver cards.

Twisted pair video transmission (UTP)

This contribution is courtesy of my colleague Renato Bordin.

Video signals from cameras are transmitted to the receiving end via coax cables, normally RG59, RG11 and so on. The camera’s composite video output buffer has a series output resistance of 75Ω and requires an end of line load impedance of 75Ω, hence all video equipment such as matrices, DVR’s, monitors etc have a cable termination of 75Ω to match the cable and camera specifications. This transmission method is referred to as an unbalanced signal path and requires a return path which the coax cable provides in the form of the screen or braiding. The concept is the same as a light bulb connected to a battery with two wires, remove one wire and the bulb stops burning since there’s no electrical connection to complete the current flow. This method of video transmission has one major disadvantage; the video is referenced to ground making it susceptible to common mode interference and provides a path for potential differences between two ground points. This often results in poor quality pictures received on the monitor and when a lightning ground surge moves between the camera and monitor the potential difference is now at a dangerous level resulting in camera failure. Other disadvantages are the attenuation properties of coax cables, RG59 for example cannot reproduce a high resolution image at 300m, the high frequency attenuation, and hence the upper end of camera resolution is reduced. The net result is a high resolution camera installed for a particularly demanding application but the received picture is in fact more a medium resolution image. Bear in mind that most applications involve a digital recording device that further reduces picture content or resolution. Digital recording devices require the highest possible camera resolution or rather video bandwidth to reproduce an acceptable image after digitization and then compression.

The alternative to using coax cable as a video transmission medium is the twisted pair cable but we have some challenges to overcome. Let’s take a look at the most popular of twisted pair cables – CAT5e, widely available and well known in the IT industry. For starters the cable impedance is 100Ω and not 75Ω as required by a camera and has no screen, so induced common mode interference becomes a problem. More importantly the cable is designed for a balanced or differential transmission method such as Ethernet and RS485/422. In the active domain differential input and output operational amplifiers (Opamp’s) are used to convert an unbalanced signal to a balanced or differential signal appropriate for twisted pair transmission and visa versa at the receiving end. In the passive world a Balun transformer is used to match impedances. In simple terms this device receives video from a camera and converts it to balanced video matched for a cable impedance of 100Ω and the receiving end converts this balanced video signal back to its original format suitable for a coax connection to the DVR, matrix etc. There are only advantages in using CAT5e cable for video transmission. 1. Since we now have balanced video, common mode interference is rejected far more than coax, resulting in less noise present on the picture. 2. CAT5e cable frequency response specifications are ideal for video so longer cable runs are possible. RG59 cable runs must not be longer than 220m – 250m using high quality cable but CAT5e cable runs can be at the 300m mark and up. 3. Since CAT5e has 4 twisted pairs, one cable can carry 4 video signals. 4. Some twisted pair video solutions have full ground loop isolation. 5. Installation ease and costs are less than a coax based installation. I’m sure several installers reading this can see several other installation related advantages.

The VIDEO CAT range of products available from BFR Digital currently includes the VC-01, a direct camera mount twisted pair converter and the VC-016R. This is a 16 channel rack mount version with full ground loop isolation. Both products feature BNC’s for camera or head end video connections and terminals for twisted pair connections.

Renato Bordin

http://www.bfrdigital.co.za/videocat.html

Why AM modulated analogue multimode fibre optic video transmitters are smaller than digitally encoded multimode fibre optic video transmitters?

I think the best way to explain this is with a few block diagrams and some photos. The block diagram below shows the basic design of a simple AM modulated fibre optic transmitter.



Our first fibre optic transmitter released in 2002 ran on this exact design and below I include a photo of this product’s PCB (Printed Circuit Board).

As you can see the design is so simple that the product is a mere 35mm in length.

A digitally encoded fibre optic transmitter is more complicated because all the video and data signals have to be converted into digital signals before they are processed and transmitted. The block diagram below shows the basic system design for this type of product.

As you can appreciate this is a far more complex design. The picture below is of our VTXD-030-SMM. When we designed the VTXD-030-SMM we decided to make the video transmitter and the video/data transmitter a one PCB design and only populate the component required for the particular model. It is for this reason that our video and our video/data units are the same size. This was done to simplify the product range and to decrease the cost of the product.

This product is 133mm in length, which is 98mm longer than the simple analogue design.

http://www.BFRDigital.co.za/fibre.html

BFR Digital Advert

I am absolutely overwhelmed by this advertisement that our marketing team and our advertising agency put together. Please click on the advert above and have a look at it in its original size.

I think it’s fantastic. It delivers a simple and clear message.

Well done to both our marketing team and our advertising agency! :-)

Let me know what you think.

Field-Lite Termination Enclosure

This is one very cool piece kit!!! 4 multimode video transmitters, 1 multimode data receiver with power supply and splice cassette in one field enclosure.
When I first designed the Fibre Pro Field Termination Enclosure (FIELD-ENC) I never thought it would be as popular as it is. This popularity has led to the DTX-Adaptor, which is an adaptor plate to accommodate the DTX Series equipment in the FIELD-ENC.

Now with the Fibre-Lite Field Termination Enclosure (FIELD-LITE), I took a completely different approach. As you can see, I designed this product to be modular. The base of this product is a motherboard which includes the power supply for the transmitter/receiver fibre optic modules; 4 output data channels to control PTZ cameras and a 12-way splice cassette. On to this motherboard, up to 5 multimode fibre optic modules can be plug-in. The modules could be 5 video transmitters OR it could be 4 video transmitters and 1 data receiver. The data from the data receiver is distributed and offers one output per video channel. All this is housed in a IP55, self-extinguishing plastic enclosure according to IEC60695-2-1 standards.

http://www.BFRDigital.co.za/

Fibre Lite

We at BFR Digital have just completed our Fibre Lite product range. This range of products caters for the transmission of CCTV video signals and unidirectional data signals over multimode fibre optic cable. Fibre Lite offers an optical budget of 12dB; which means a maximum cable distance of 2.5km and a system safety margin (excess power margin) of 3dB.

This product range is the first in its class to feature Digitally Controlled AGC; this feature automatically adjusts the AGC to compensate for optical cable degradation and other insertion losses. Each video receiving channel has it own dedicate processor that continuously samples and adjusts the AGC.

In true BFR Digital fashion the Fibre Lite range is designed to be robust and easy to use; for this reason the Fibre Lite range is offered with a 2 year warranty. We achieve this robustness and reliability by over engineering our products.

www.BFRDigital.co.za