Mar 19

What fiber connector should I use?

Over the past couple of weeks we talked about the tools needed to troubleshoot fiber connections on the LAN along with methods of troubleshooting those connections. This week I want to talk about the fiber connectors.
At the end of every fiber there is a connector. This connector is very important. The connector needs to match your optical module or your patch panel. The wrong connector will not work well, or may not work at all. Here is a list of the most common connectors that I have experienced in my carrier.


ST – These are very common on older equipment and patch panels, they are the ones you push in and twist into place.
SC – These are common today. Many optical modules still use these connectors.
LC – These connectors seem to be today’s standard for use on optical modules and patch panels. They are the smallest and therefore more can fit on a line card.

The end of the connector where the light is omitted is polished. This polish has different levels of back reflection (This is where the light would bounce off the end of the fiber and go back to the source. Measurement of light off of the connector).

In General, you only need to be concerned with the polish on Single-Mode connectors. The connectors that I have used have always been SC. The three polishes are Physical Contact (PC), Ultra Physical Contact (UPC) and Angled Physical Contact (APC). The proper term for the connector would be an SC/UPC or SC/APC. UPC connectors are usually blue and usually have blue barrels in the patch panel. APC connectors are usually green and usually have green barrels in the patch panel. If you look at the tip of the APC connector you can see that it is angled instead of flat on the UPC. The color of the patch panel does not matter; it simply helps you identify the connector type.

I have seen both UPC and APC be used in large fiber plants. Some locations would use SC/APC, others would use SC/UPC. As long as the connectors match up, it usually doesn’t matter what is used. If there is ever a choice, you should use the APC connector because it produces less back reflection. Due to a lack of correct fiber jumpers, I have made a good connection with an SC/APC and an SC/UPC before. The connection degraded the signal, but the link came up. Unless you are in a bind, I don’t recommend doing this.


I have only had one instance that truly required the APC connector. I was using a single strand Single-mode optic. The transmitter and receiver were on the same fiber and when the laser hit the end of the UPC connector it would bounce back. The receiver would see it’s own light and it would tell the switch that the link was up. As you probably imagine, this was a problem. Once identified, APC connectors were used and the reduction in back reflection resolved this issue.

When you connect a fiber into a piece of network equipment you always use a PC or UPC connector. I have never seen a requirement for an APC connector by a hardware manufacturer.

Instead of pictures for you, I found a nice video from L-Com that does a good job of showing the connectors. Please click here to see the video.

What experiences have you had with APC or UPC?
Why did you use one over the other?

Sep 08

What it takes to get into the networking field

I have read many forum posts about people wanting to get into the networking field and how to do it. I believe that the networking field is a great field to work in. Some times the hours are rough, but it’s well worth it. Here are my suggestions on what to do in order to get into the network field.

1. Be willing to learn, and continuously learn. Network vendors continue to come out with new equipment and new protocols. Each time, there is more to learn. I recommend reading in detail about each and every device on the network. As a network engineer you need to know what the limitations are of each product and module or line card in each product. You need to know where the over subscription is in your equipment. After 12+ years in the networking field, I continue to read release notes and configuration guides of each platform, even if it’s from the same vendor.

2. Get the basics. In the year 2000 I graduated from Illinois State University with a BS in Computer Science. I had a couple of programming classes, the rest were networking and telephony classes that taught me the basics. I learned about parity, IP, TCP, ASCI, TDM, Network Modeling, bottlenecks etc.. I even learned how to count in Base2 in order to understand IP addressing and why all of the numbers are divisible by 8. All of these basics still apply today. With out the basics, I would not be able to troubleshoot issues as well as I can today. I suggest finding a community college to take some courses that will teach you these NON-Vendor specific basics.

3. Vendor and Part specific knowledge. You need to get hands on experience and training on specific equipment.

There are a large number of community colleges that have CCNA (Cisco Certified Networking Associate) classes. I suggest taking one of the classes that are spread out over several weeks. Week long classes are very difficult and it doesn’t give you time to learn at your own pace. I worked with a guy that took week long classes and got his CCNA and CCNP certifications from these classes; he forgot everything and wasn’t worth the money we were paying him.

4. Get a JOb!!! Get an internship or a entry level position. Find a place that is willing to train you and allow you to work and grow. You may have to take less money then you make, but it will be worth it. If you continue to improve your skills, your salary will increase over the next few years. Don’t ever take a job at a company thinking you are getting your foot in the door with hopes that you will move into the networking group. Most likely, you’ll forget what you learned and not achieve your goal.

I had a guy tell me one time that he got out of IT because he was tired of learning something new every day. If your not willing to learn something new everyday, the Networking field is not for you.

Please give me your feedback about how you got into the networking field, or if you found this to be helpful!!!!!