Over the past 15 years, I have helped hundreds of clients with their network design, planning, and associated fiber management needs. These networks range from the CATV HFC boom days of the mid-90s, through the fiber escape scenarios of telcos, to the gigantic bandwidth needs of various FTTH deployment strategies. One of the constants in all of them has been the consideration of link loss budget planning: How far can I go with my current optical power before having to terminate or amplify? It has always amazed me that more often than not, the first response to distance limitation is to put more optical power in the path of EDFAs, transmitters, and amplifiers. Optical transmission and having the power to get it where you want it can be a costly affair. However, increasing power isn’t the only way to gain distance.

Perhaps the most overlooked element in network design is the quality performance of a single element: the fiber patch cord. A quality patch cord not only improves network performance and reliability, it also increases the dollar value of current active optical equipment already installed in the network. The key to optimizing your network value proposition is to require a downgrade. dB loss in each installed patch cord.

During my years in the industry, I have often seen loss quotes for coupled pairs (two connectors or ends coupled through an adapter). 6dB per pair. In a logical fiber run that included 10 end-to-end coupled pairs, I had to assume 6 dB (0.6 multiplied by a factor of 10) of loss at the connectors alone; that is before calculating the loss associated with fiber length, active equipment, optics components and splices.

In recent years, Telcordia has established that the dB loss standard should be no greater than .4dB. If you could achieve a 50% improvement in insertion loss across all your patch cords, think what that could do for your optical budget…

Using the same example of 10 coupled pairs in a fiber logic run; can gain 2dB of optical power. Think of the cost difference of going from 19dB to 21dB optical launch power versus upgrading your patch cord performance standard to 0.2dB insertion loss, without increasing the price. Assuming 0.20dB of loss per kilometer at 1550nm (without any splice loss), the increased performance of the hose allows you to extend your existing power by almost another 10 kilometres. At a minimum, it gives you some optical headroom to insure against further dimming events that occur after installation.

Guaranteed vs. Typical?

When Telcordia reset the standard to 0.4 dB loss, most patch cord vendors reported “typical” performance levels of the Telcordia standard. As “typical”, the process to build the patch cord was able to deliver 0.4 dB throughput, but each individual patch cord that came off the line may or may not meet the standard: 51% of patch cords met the standard? standard? 75%? Few patch cord vendors were “guaranteeing” 0.4dB loss, as it required extensive quality control measures in their production process and very tight tolerances in their test metrics. These changes were perceived by the provider as expensive and cost prohibitive. Achieving a “guaranteed” level of performance was expected to result in a large amount of “junk” on the production floor, as patch cords that did not meet the guaranteed number were either reserved as “seconds” or re-polished. to achieve the desired results. With no certainty of what they were getting, network designers needed to allow for variation in the performance of patch cords. As a result, their network designs were unable to fully benefit from the reported performance improvements.

Setting a new standard

Fiber in the outside plant has made guaranteed performance critical to network design. Fiber reach, guaranteed for immediate and continuous performance over the life of the network, is critical to delivering the user experience that FTTp networks promise. As a result, a new class of patch cords is emerging that ensures deep performance in the fiber network. Suppliers that have built their manufacturing plants for optimal performance are delivering guaranteed loss.2dB.

Guaranteed loss of no more than 2dB reduces the cost of FTTp network implementation by extending the reach of the network, minimizing the need for amplification at output ports or EDFAs, and allowing network designers to focus on other elements of your network design. What’s more, manufacturers of this new class of hoses offer this level of connectivity without a significant cost premium due to repeatable processes that have been established within their world-class factories. FTTp network designers now have a lot to get excited about!

So how do you know if you’re getting the quality patch cord you need for your network?

Step 1 – Demand 100% of. 20B or better. Period. This requirement alone will eliminate World Class hopefuls.

Step 2 – Ask a few simple, but critical questions about processes, systems, and people to ensure a quality-driven, repeatable manufacturing environment exists.

Can you tell me the types of automation you have built into your completion process?

While fiber termination requires many manual processes that must be performed by qualified technicians, there are many things to look for in your manufacturers’ processes that automate critical steps in the fiber termination process.

examples

Epoxy – What type are you using? Mixed, premixed? How do they degas? This is critical for termination used in uncontrolled environments such as outside plant. Some will cheat on this step. They may give you excellent performance data. But will it work properly in harsh environments?

Epoxy Dosing – How is the volume rate controlled? A simple syringe is often used and dispensed based on the visual judgment of the personnel performing the job, which can result in variability in the volume of epoxy dispensed. Look for control here with manufacturers that use pneumatic syringe dispensing equipment that is also equipped with timers. Epoxies exposed to oxygen will cure and become unacceptable for use over time. Again, performance data may look good, but long-term reliability can suffer if epoxies are not handled and proportioned correctly.

Hackel removal: A very critical part of the process, as a good or bad hackel removal is not discovered until the end of the termination process in test and visual. Most manufacturing environments use a manual process whereby a scribe is used to score the glass next to the ferrule and break it. A better process is to score the glass on two sides 180 degrees apart and remove the stinger rather than breaking it. This minimizes change due to cracks only found in the test. The best way is to use automation by means of a laser cutter. This process uses a controlled laser to cut/melt the stinger away from the ferrule to very close tolerances, eliminating a manual epoxy removal step that can also cause cracking.

End Face Inspection – This is the process of checking an end face for pitting, scratches, cracks, and particles. Do you have one? Many don’t. If they can get the connector up to performance, they’ll call it good. While there is no recognized industry standard for the condition and cleanliness of end faces, there is no question that long-term reliability is greatly compromised in a dynamic connector, as pitting and scratches can collect particles that can contaminate other connectors. For those who have a standard endpoint, ask if it is subjective to an operator or if automation is used with a digital image of the endpoint, magnified at 400x, compared to a profile that has been previously loaded into the equipment and only delivers one condition pass or fail. Ask to see this profile which tells you exactly what kind of defects they will allow. No pits or scratches should be allowed in the contact zone 1, 2 or an area 8 times the size of the core. This type of process ensures reliability long after performance data is measured at the factory.

Performance tests: at what wavelengths are they measured? Performance is more sensitive at higher wavelengths. Namely. 1550 and 1625. Insertion loss must be equal to or better than x. These are not “typical” results. The loss must be measured at each termination and not be a total or average sum of the patch cord.

End Geometries – The interferometer is an absolute necessity for developing a polishing process and then to ensure that the process remains capable. Anyone who tells you they don’t have one should quickly walk away. Ask if any of their geometry standards exceed Telcordia’s industry standards. If you really want to get into the process, ask to see the distribution of key geometric data such as radius of curvature, apex offset, and fiber undercut/bulge. It is the average in the range or right in the middle of the norm. In short, they’re passing but “living on the edge” You could plot your own histogram and check… OK, I’m getting carried away here and these are supposed to be fast.

Are you ISO certified?

This is another “elimination” question. While a “no” answer does not necessarily mean that they cannot deliver a quality finish, a “yes” indicates that they have quality systems in place for documentation, processes, training, and a variety of controls for a manufacturing environment. quality.