VOSCOM Fiber Optics Blog

When implementing a fiber optic transmission system, several factors need to be considered. Included are: fiber optic transmitter output, fiber optic sensitivity, fiber losses and bandwidth, losses from splices and terminations; over all distances – see figure (1).

Figure 1. Optical System Design Consideration

1. Determine the correct optical transmitter and optical receiver based upon the signals to be transmitted – video, audio (bal/unbal 600, unbal 10k or 47k Ohm) data (over the Coax as Coaxitrontm and Proteustm , Manchester, Biphase, RS-232, RS-422, RS-485, Sensornettm, Ethernet, TTL, Open Collector or Contact Closure);

2. Determine the operating power available at remote locations (24VAC, 12VDC) and at the control rooms (120V, 240V);

3. Determine the type (multimode or singlemode) and number of available fiber strands and optical connectors installed on the cable (ST or FC);

4. Calculate the total optical loss (in dB) in the system from end to end; include cable, splices, patch panels and connector losses. Parameters should be available from the manufacturers of the optical cables, fiber accessory hardware (patch, splices) and/or the sub contractor who installed the cable network;

5. Compare the loss figure obtained with the optical loss budget of the electronics as per the manufacturer’s specifications. In order to account for ageing of light sources, add a safety margin factor of 3 dB to the entire system.

6. When transmitting multiple high bandwidth signals, as in video multiplexers, compare with the available bandwidth in the fiber, to ensure the signal will be transmitted.

Example # 1: we have a requirement for transmission of 1 video signal with bi-directional PTZ data, there is one fiber available and the distance required is 13,000ft or a little less than 4Km (1Km = 3381ft.). As the signal is carried through several buildings, there are a total of 6 patch panels from end to end. Let us assume the loss of the video/data link is 13dB and the center carrier is 70 MHz. The specifications indicate that the video signal is transmitted @ 1300nm and fiber loss and bandwidth are specified @ 1dB and 500 MHz, respectively. NTK3631 Series transceivers are specified.

Distance required is 13,000ft. or 4Km

Calculation # 1 – as to loss budget

Fiber rated @ 1dB loss per Km x 4 Km, loss in cable = 4dB
Connector loss is system @ 1dB/connector x 2 = 2dB
Patch Panel loss in system @ 0.5dB/adapter x 6 = 3dB
Safety Margin = 3dB
Total Loss = 12dB
Since the 3631 Series link budget of 13dB is better than the 12dB the system requires, the conclusion is
that, based on loss, video/data signals may be transmitted on the 1 fiber.

Calculation # 2 – as to available bandwidth
Fiber optic Bandwidth per Km @ 1300nm = 500MHz
Divided by Bandwidth of 3631 Series System = 70MHz
Total Distance System may Transmit = 7 Km
Since the video/data signals use 70MHz, one simply divides the available fiber bandwidth of 500 MHz by
the system bandwidth of 70MHz. The result indicates that, based on bandwidth, the video/data signals may
be transmitted on the existing fiber.

Example # 2: we have a requirement for transmission of 4 video signals, there is but one (1) fiber available and the distance required is 10,000ft or a little less than 3Km. As the signal is carried between two buildings, there are two (2) patch panels – one at each end. Let us assume the loss budget of the video multiplexer is 10dB and carrier (combined bandwidth) of the 4 video signals is 150 MHz. The specifications indicate that video signals are transmitted @ 1300nm and fiber loss and bandwidth are specified @ 1dB and 500 MHz respectively. NTK3644 Series transmitters and receivers are specified.

Distance required is 10,000ft or 3Km

Calculation # 1 – as to loss budget

Fiber rated @ 1dB loss per Km x 3 Km, loss in cable = 3dB
Connector loss is system @ 1dB/connector x 2 = 2dB
Patch Panel loss in system @ 0.5dB/adapter x 2 = 1dB
Safety Margin = 3dB
Total Loss = 9dB
Since the 3644 Series link budget of 10dB is better than the 9dB the system requires, the conclusion is that,
based on loss, 4 video signals may be transmitted on the existing fiber.

Calculation # 2 – as to available bandwidth
Fiber Bandwidth per Km @ 1300nm = 500MHz
Divided by Bandwidth of 3644 Series System = 150MHz
Total Distance System may Transmit = 3.33 Km

When fiber is rated @ 500MHz per Km, it does not mean that for every new Km, there is an additional 500MHz. Since the 4 video signals use 150MHz, one simply divides the available fiber bandwidth of 500 MHz by the system bandwidth of 150MHz. The result indicates that, based on bandwidth, the 4 video signals may be transmitted on the 1 fiber. If, after performing the calculations, it is discovered that the loss is greater or bandwidth is inadequate, it will be necessary to consider the installation of additional fiber.

Typical Applications

The following chart of typical applications includes the reasons, advantages and benefits when fiber optic transmission systems are installed over copper twisted pair or coaxial systems.

CCTV and surveillance technology is constantly evolving and today’s digital IP cameras provide increasingly sophisticated capabilities for monitoring, recording and reviewing activity inside and outside your property. With a wide choice of products available, understanding your options can be confusing, whether you’re new to CCTV or planning to upgrade an existing system. Here are the top ten things you need to ask yourself to get the right CCTV system for your needs.

1: Defining criteria – Why do I want to install CCTV?

It’s essential to start with a clear idea of what you want your CCTV system to achieve. What suits your neighbour or another business may not suit you. Are you considering the investment as a deterrent to intruders and thieves? To record access to a building or car park? To monitor movement in particular areas of your property? To record activity round the clock or at specific times, for example when your property is unoccupied? You also need to think about what you want to do with the information once you have it. How long do you want to keep it? How often do you want to review it? With clear objectives, it’s easy to determine the criteria – such as picture resolution, camera focal length and image storage requirements – that will ensure your chosen system is fit for purpose.

2: Basic requirements – What equipment will I need?

Essentially, a CCTV system comprises one or more cameras and either a software- or hardware-based image recording facility. Until recently CCTV cameras operated by transmitting analogue video signals through copper cables or fiber optic cable to a central location where the video signal was recorded. While analogue cameras still have their place, today’s more sophisticated IP cameras produce digital output and use IP networks to relay their images. The number and type of cameras you choose will depend on the subject and the extent of the surveillance area.

3: Recording options – How can I store images?

Images can be stored on the camera itself, on a computer or on a digital video recorder (DVR). The output from an IP camera is digital and is recorded without change; the output from an analogue camera is first digitised and then stored. DVRs and computer software offer the ability to record multiple channels, ie images from several cameras at the same time, regardless of the camera type. With analogue cameras, the number of channels that can be recorded is limited by the number of physical connections on the DVR, whereas in an IP system it is usually limited by software licensing. The number of camera sources you want to record from, the image quality you require, and the length of time that you want to store those images will all influence which recording device is best for you.

4: Ongoing surveillance – How can I monitor images?

A key consideration in getting the right system is to know how you want to view the images from your cameras. Will you have a central control room with trained operators constantly monitoring screens? Do you want a third-party to monitor your property? Will you want to access your CCTV images remotely while abroad? Do you want to receive email or text alerts if suspicious activity is detected by your CCTV system? IP cameras can be connected to the internet to relay images anywhere, and both IP cameras and DVRs have the capability for motion detection.

5: Static or not – Do I need fixed or moving cameras?

Camera housings can either contain fixed cameras, trained on a single location, or PTZ (pan/tilt/zoom) cameras that can rotate 360° and provide pre-programmed ‘tours’ of an area. Motion detectors can be added to a PTZ camera system so that the camera can respond and focus in on suspicious activity. Depending on the rationale for your CCTV system, you might want a mixture of fixed and PTZ cameras to cover different zones and applications.

6: Camera features – Do I need IP or analogue cameras?

While an analogue camera is ideal if you want to monitor one location from a fixed position, an IP camera is more flexible and can enable more sophisticated surveillance, recording and review. IP cameras can deliver high definition or megapixel images, which give greater detail and can cover a greater range. They can also be powered over a network using Power over Ethernet (PoE), so do not require a separate power supply. Some IP cameras have audio recording built in which allows recorded messages to be broadcast automatically to warn people that they are being watched. However, this functionality can be integrated into any camera’s housing and is not a specific benefit of IP. Both types of camera can also feature infrared technology to capture full-colour images during the day and black-and-white images in low light or even complete darkness.

7: Intelligent security – Should I integrate my CCTV with my other security systems?

CCTV cameras can be easily integrated to enhance your security. When integrated with an intruder alarm, your CCTV system can be set to record images at a higher resolution when the alarm is set or activated. When integrated with an access control system, CCTV can provide additional visual verification that a person has authorised access. Your specific integration requirements will influence the type of camera and recording equipment you need.

8: Investing wisely – How do I make the most of my budget?

This depends on what you want your CCTV system to achieve. IP cameras are more expensive because their image quality is better and they are more flexible, but analogue cameras are often sufficient for the job. If you only need fixed-point monitoring, a low-spec, low-cost analogue system would be the right choice. On the other hand, if you need to monitor a large area, it may be more cost-effective to use one high-resolution PTZ camera in the place of several fixed analogue cameras.

9: Going digital – Should I upgrade to a digital system?

The need to upgrade will depend on what equipment you already have, your surveillance requirements and your budget. By replacing a VHS video recorder with a DVR, the feed from existing analogue cameras can be digitised and more easily stored. The system can then benefit from features, such as motion detection, which are supported by DVRs. IP cameras can also be introduced to work alongside analogue cameras allowing you to benefit from their technology where appropriate.

10: Industry validation – What accreditation or references should I look for in a CCTV installer?

Credible CCTV installers will have industry accreditation such as recognition by the NSI (National Security Inspectorate) which promotes compliance with relevant British and European Standards as well as the requirements of the police and the insurance industry. A reputable company will not have any problem with you asking for their credentials, and should also be able to introduce you to existing customers for reference.

Unless you have received a personal recommendation, choosing a security company can seem daunting. Searching on the internet can present you with a wide choice of companies, all seeming to provide what you want. So how do you decide which one to choose? Your success in making the right choice depends on two key activities: thoroughly researching what functions and service you will get in return for your investment, and correctly assessing the expertise and professionalism of the company you choose. Here are the top ten criteria you need to investigate along with the questions you need to ask to be confi dent of making an informed decision.

1: Reputation – How long have you been in business?

A company that has been in business for some time will be well-tested and have a relatively large customer base. It is also more likely to be able to weather a diffi cult economic climate and less likely to fold leaving you to repeat your selection process or write-off any of your investment. Can the company tell you how many customers it has? Can it provide you with customer testimonials?

2: Product knowledge – What product ranges do you use?

Products and technologies are constantly changing. Try to establish how knowledgeable your prospective security company is, what product options and choices are available to you, and how the company embraces new technologies. Ask what areas of security it covers – alarms, access control, CCTV, and so on, and be confi dent that they can meet any future requirements you may have.

3: Customer-centric advice – How do you decide what is best for me?

A company that sees itself as a trusted advisor should help you decide what’s right for you and not try to impose a one-sizefi ts-all solution – the right solution might not necessarily have all the features that are available. Make sure when you receive your estimate that the company has really listened to your requirements and taken into account your budget and any other constraints you have stipulated. If you are in a listed building, you might want to deal with an installer that has experience working in this kind of environment and understands the challenges it may present.

4: Breadth of service – What sort of ongoing customer care do you provide?

Regular maintenance of your security system will ensure peace of mind and should avoid the need for expensive
emergency call-outs. Reputable companies will offer a range of service levels to suit your budget and the system being
installed. They should be able to offer a committed date and time for maintenance visits. Ask whether there is a dedicated customer service function and fi nd out how they handle customer calls out of offi ce hours – do you have to call a mobile number or is there seamless continuity of service via a landline? Will they come out at weekends? Do they guarantee 24/7 support 365 days a year?

5: Tailored security – Can you offer a system design service in-house?

If you have more complex security requirements, you will probably want to choose a security company with a specialist design team, experienced in producing bespoke solutions. These specialists should also be able to advise you on legal requirements (such as privacy issues related to CCTV), and health and safety issues. The better companies will be able to create CAD (Computer-Aided Design) drawings so that you can properly visualise the fi nal installation and can accurately assess the impact and viability of different options.

6: Staff quality – How do you ensure your employees are trustworthy and competent?

The staff of your chosen installer may come into your home or business and have access to passwords and security codes to physical areas and computer systems. You need to be absolutely certain that they are trustworthy. Does the company carry out police checks on its staff? Equally important is the staff’s ability to resolve problems and deal with any issues you may have. How does the company train its staff? Is it endorsed by any third parties such as Investors in People, the national standard for investment in training and development? You may also want to check how the company complies with health and safety requirements, and the levels of public and product liability insurance it carries.

7: Responsiveness – How quickly can you get back to me?

Asking for a quick turnaround on your quote can be a simple and effective way of assessing how rapidly the company is likely to respond if you need to call on it in future. Can they give you a price the same day or next day? Ask what their process is for responding to emergencies. Do they guarantee response time?

8: Total cost of ownership – What additional charges am I likely to incur?

Don’t automatically plump for the company which comes in with the lowest quote. It is highly likely that a company charging more will also give you more in the long run. Ask for a detailed specifi cation of the equipment and ask whether you will own the equipment or be leasing it. Secondly, fi nd out if the cost covers other customer and support features such as technology upgrades, handover training, and ongoing maintenance and monitoring. You should also check how long the warranty lasts and what exactly it covers. What, for example, will happen if something goes wrong and you need to call someone out as an emergency – how much will you be charged? For commercial installations, can the company provide training to new staff in the future?

9: Industry validation – What industry accreditations to you have?

If the company has a sound foundation and follows best practices it will no doubt have some sort of industry accreditations. There are several badges that you could look for but some of the best are Gold awards from the NSI (National Security Inspectorate) which promotes compliance with relevant British and European Standards as well as the requirements of the police and the insurance industry, and membership of the FSA (Fire and Security Association) which works to improve professionalism in the industry by supporting the development of technical and occupational standards, apprenticeship schemes and training programmes. A reputable company will not have any problem with you asking for this information.

10: Testimonials and references – Can I speak to your existing customers?

There are two advantages to being put in touch with a company’s existing customers. One is that it demonstrates the company’s confi dence in its work and service. The other is that it gives you an opportunity to delve a bit deeper into what level of service you can expect. Clearly the company is unlikely to get you to speak to someone who says they wouldn’t recommend it, but you can look into how smooth the whole process was by asking about aspects such as how the company behaved if they were going to be late – did someone phone to let the client know? Was anything damaged during installation and, if so, did the company make good? Most importantly, would the customer use the company again?