Welcome, let's brush up on some Fiber basics.
As fiber first rolled out, fiber splicing was as much art as function, microscopes and cameras were bulky, LED's were expensive and each fusion splicer hand tuned. The machines modernized with the industry with better CCTV cameras, smaller mirrors, more automatic positioning techniques -- the original form may have shrunken but has remained virtually unchanged as economy of scale techniques have been used to bring down overall system prices.
Not a huge surprise when you consider most product testing is done in a lab environment by lab techs for white coat inspectors. In our service lab we see a dozen different splicers from as many as seven different manufacturers every day: profile alignment, LID, core alignment, V-groove, 60 pound beasts from the early days, and even today's small 'handhelds' that splice a dozen times and then beg for a new battery.
With brighter LED's why are there still mirrors to clean? With the advent of better definition CCTV chips why are multiple cameras still required? With a steady movement toward uniformity of raw fiber production, why are all the dust attracting gels, sprays and clamps even necessary anymore?
A fiber splicer's laboratory is his or her truck, or its tailgate on a good weather day. With the plethora of units available for sale these days, it's hard to determine what features and tech you need.
If you’re new to fiber or just brushing up before your next project bid, here are some common fiber optic basics. Let's dive into some Fiber basics to help you become more familiar.
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What is Optical Fiber?Fiber is made up of a core surrounded by a cladding layer. Both are glass but each has its own index of refraction.
Basic Types of Optical FiberIn use today are two general types of optical fiber:
Singlemode (SM) fiber is designed for use with a signal of one wavelength of light, typically at invisible 1310, 1480, 1550 or 1625nm wavelengths. Most often with a core diameter of 250µ (micron), singlemode fiber is commonly used for long distance regional or inter-city transmissions of data.
Multimode (MM) fiber is based on the ability to combine different wavelength signals in the same fiber path, typically at invisible 850 or 1300nm wavelengths. Most often with a core diameter of 900µ (micron), multimode fiber is commonly used for short distance curb to house, or patch cable transmissions of data.
Fiber Optic Fundamentals
Fiber optic lines are made up of a core surrounded by a cladding layer. Both are glass but each has its own index of refraction. The light signal is applied to the end of the optical fiber and then bounces down the optical path.
Singlemode fiber is designed for use with a signal of one wavelength of light, typically at an invisible 1310 nm, 1480 nm, 1550 nm or 1625 nm wavelengths.
Multimode fiber is based on the ability to combine different wavelength signals in the same fiber path, typically at an invisible 850 nm or 1300 nm wavelength.
Common signal connection between transmission systems use ST or SC for multimode (generally jacketed in orange protective cabling), ST, SC, FC and LC for singlemode (generally jacketed in yellow protective cabling). Angled connectors are also prevalent in cable video applications: ASC or AFC (generally color coded green for quick identification).
Typical multimode connection losses are 0.2 to 0.5 dB, singlemode connection losses typically 0.5 to 1.0 dB - this is why even today so many inside applications show a preference for multimode connections requesting pigtailing.
Joining Fiber Optic Cables
There are two ways to join fiber optic cable (working with glass fiber, of course, you can't twist it together or tie it in a square knot):
Mechanically - Two finely polished fiber ends are mated in a mechanical device with a small amount of index matching gel.
Arc fusion - Simply cleaving and melting the two fiber ends into one solid glass fiber to ensure minimal loss.
Typical mechanical connection losses are 0.3 dB and fusion are 0.03 dB. These losses, plus the typical loss of the fiber type you are using should fall within the loss budget.