C H A P T E R
9
GUIDELINES FOR
FIBER OPTIC DESIGN
AND INSTALLATION
ERI C PEARSON
GENERAL GUIDELINES
Use these guidelines for evaluating and comparing vendors, choosing products,
and evaluating options and cost impacts of your decisions.
1. Start with a list of specifications. After the cable plant is designed, but
before you contact any manufacturers, copy the information you have
generated onto a specification summary sheet so you have all of the spec-
ifications for each component conveniently available when talking with
potential suppliers.
2. All performance numbers need test specifications. In addition to learning
whether the numbers are minimums, maximums, or typical perfor-
mances, you need to know how the numbers were determined. When
comparing products from different vendors, be certain that the specifica-
tions are the same, so that you know that you are comparing apples to
apples.
3. Talk to at least four vendors for each component. Remember that the
fiber optic industry is highly competitive. You will be able to ask for, and
115
116 CHAPTER 9 GUIDELINES FOR FIBER OPTIC DESIGN AND INSTALLATION
usually receive, the best price possible, even though you may be compar-
ing several products that are not identical, such as cables or connectors.
Remember to ask the question Why should I buy your product instead
of another supplier s product? The answer to this question may include
mention of other suppliers or of equivalent products.
4. Talk with representatives more knowledgeable than yourself avoid the
blind leading the blind. By this step in the process of designing your
fiber optic system, you should be more knowledgeable than many of the
individuals selling fiber optic products. Therefore, when you need infor-
mation, deal with people who know what they are talking about, even if
you have to bypass the salesmen or representatives and talk directly with
the factory.
5. Expect and resolve conflicting facts/opinions. At this step in the process
of designing your fiber optic system, you have defined the performance
criteria that will result in the lowest-cost fiber optic system possible.
Now, you need to find sources for the components for which you have
specifications. Be aware that you will probably learn from potential sup-
pliers some facts that differ from the facts and information you may have
learned elsewhere. Expect this to happen. When it does, you should
resolve these differences.
6. Use the five-year rule. Unless you have an excellent and compelling rea-
son not to do so, deal with suppliers who have been in business for at
least five years. Such companies have been in business long enough to
know how to avoid most of their problems, how to guide you to avoid
your problems, and how to be around in another five years (when you
need repair or some other support).
7. Use the high serial number rule. Unless you have an excellent and
compelling reason to do so, avoid buying a product with a low serial
number [or kilometer number]. For any product other than the most
simple, you are less likely to experience problems if the serial number is
100 than if it is 11. This and the previous guideline should not limit the
number of vendors who can supply what you need. When talking with
potential suppliers, ask questions such as How long have you been mak-
ing this product? How many customer returns or field problems have
you had with this product? and How many kilometers have you made of
this product? The answers to these types of questions will help you eval-
uate the reliability, workmanship, quality, and delivery considerations
that you will use in deciding on a supplier.
8. Know the cost impact of your design decisions. Know or learn the cost
impact of your choice of one design over another. This guideline applies
equally to optoelectronics (wavelength of operation and light source-LED
CHAPTER 9 GUIDELINES FOR FIBER OPTIC DESIGN AND INSTALLATION 117
or laser diode), to connectors (ST versus ESCON or FDDI), and to cables
(loose tube versus breakout distribution).
9. Buy only the performance you need. Do not be influenced by an answer
that includes any phrase such as our product has higher or better per-
formance that justifies its higher price unless you need that better
performance. In general, most products available in today s marketplace
exceed the performance needs, either in distance of transmission, or of
bandwidth, or of accuracy of transmission, of most applications. You
will gain nothing by paying a premium price for higher performance
that you will not use.
10. Ask for competitive information. Ask questions such as Who is your
competition? Or Who do you compete against? You may not get an
answer, but sometimes you will find new suppliers this way.
CABLE GUIDELINES
1. Ask for product close to your needs. After you have presented your list of
specifications, ask whether each supplier has any other products avail-
able at a lower price. Cable manufacturers will often have leftover
lengths, lengths with a single broken fiber (for example, 1 broken fiber
out of 12 when you need 10), or lengths with one fiber with an attenua-
tion rate higher than the specification for which it was originally manu-
factured. These types of products may well suit your needs. They can
often be purchased at a significant savings over the exact product you
need, if they meet your needs without compromising performance.
2. Look for the best price possible. The fiber optic cable industry is highly
competitive, so you will be able to get a good price by shopping around.
It has been our experience that at any point in time, there is always some
manufacturer hungry enough for business to offer exceptionally low
prices. In some cases, manufacturers have been selling cable at a loss in
order to capture market share. You should contact at least four suppli-
ers, but should not need to contact more than seven or eight in order to
get the best price possible.
3. Be cautious about premium prices. Be cautious about paying premium
price for premium performance, unless your design calculations support
this need. Most data communication applications do not use the optical
power budget available or the bandwidth distance product. Before pay-
ing premium prices for premium bandwidth-distance product (BWDP),
be certain to perform the effective bandwidth calculations. These calcu-
lations will demonstrate that 850-nm operation usually does not justify
premium BWDP. These calculations may justify premium BWDP for
118 CHAPTER 9 GUIDELINES FOR FIBER OPTIC DESIGN AND INSTALLATION
1300-nm operation. And you can safely assume the fiber being used all
exceeds manufacturers minimum specifications by a large margin.
OTHER CONSIDERATIONS
Of course, price is not the only consideration. Reliability, workmanship, quality,
and delivery are also important. In order to evaluate these other considerations,
we provide the following observations. We have found that most manufacturers
of fiber optic cable have about the same level of reliability and other considera-
tions. In addition, as we review the data sheets of comparable cables, we find that
no supplier has the best products. Finally, our conversations with both pur-
chasers of cables and others in our industry support this observation: Most man-
ufacturers are reasonably reliable in the products they supply to their customers.
This is as it should be, since most cable manufacturers have been in business for
at least five years.
CONNECTOR GUIDELINES
1. Are any connectors easier to install? Remember to be skeptical of any
salesperson who tells you that his or her product has the best perfor-
mance, highest convenience, or easiest installation. Most of these
statements are sales propaganda. The most accurate statement is that
some connector installation techniques are easier than others. The reality
is that there is no universally best product. All fiber optic connector
types have advantages and disadvantages, which will add up differently
depending on the factors in your specific situation. These factors are
many: product performance, product price, cost of installation tools and
fixtures, the number of connectors being installed, the level of experience
of the installer, the need or lack thereof for training, and a number of
additional factors.
2. Know about ceramic connectors. When considering connectors with
ceramic ferrules, remember that most ceramic ferrules are manufactured
by the same few Japanese companies. As such, there should be no signif-
icant price differences from different manufacturers.
3. Ease of installation may result in undesirable performance. Some con-
nectors are sold as requiring no adhesive or epoxy. The sales pitch
here is ease of installation. To be certain, the use of an adhesive or epoxy
is time-consuming and inconvenient. However, these other methods may
result in other performance disadvantages. For instance, all of the con-
nectors not requiring these materials use a clamping mechanism for grip-
ping the fiber. Use of this mechanism can allow the fiber to move into
CHAPTER 9 GUIDELINES FOR FIBER OPTIC DESIGN AND INSTALLATION 119
and out of the connector, called pistoning. In some situations, this
pistoning will not result in any problems. However, in other situations, it
will cause severe problems, including destruction of active devices in the
optoelectronic boxes. The point in both of these examples is that your
choice of connectors needs to be made on the basis of performance and
cost, not solely on the basis of style or design, and not solely on the basis
of any single characteristic.
4. There is no substitute for experience. Whatever components you choose
to generally use, you must learn how to use them and practice doing it
continuously to not lose the technique. This is especially important for
connector termination and splicing. Unless you are doing it continu-
ously, you must work your way back up the learning curve each time you
begin a new job. Your yield (number of good connectors out of the num-
ber attempted) will be a function of how much practice you have. Setting
aside some time to practice before going on a field installation may be an
excellent investment.
REVIEW QUESTIONS
1. What is the first thing needed to start evaluating fiber optic vendors,
products, and pricing?
a. How long the manufacturer has been in business.
b. A specification summary sheet for each component.
c. Alternative product options.
d. Experience with the product or vendor.
2. What is the most important thing to determine when talking to a repre-
sentative of a fiber optic manufacturer?
a. How long the person has worked for the company.
b. Who is the company s competition.
c. Is the person knowledgeable about the products and applications
such as yours.
d. all of the above
3. Which of the following are true about these connector specifications?
Ease of installation, High performance, Low cost
a. T or F: Ceramic ferrule connectors have about the same performance
regardless of cost, so you should buy for price and delivery.
b. T or F: High performance connectors are easier to install.
c. T or F: Connectors that are easy to install are more expensive to buy
but may not be more expensive when labor is included in the
cost.
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