# Monthly Archives: April 2012

## Randomly Choosing a Winner from a Weighted List with Excel

My wife is participating in a friendly contest at work that encourages employees to exercise. The employees record how many laps they walk around a set course during a month. At the end of the month, an Excel "drawing" is held to award a prize to one of the exercisers. To encourage more exercising, the likelihood of winning is to be proportional to the number of laps each person walked during the month. I was asked if I could write an Excel worksheet that would perform this task. Continue reading

Posted in software | 28 Comments

## A Little Specification Reading Before Bed

Nothing like reading ITU optical specifications to help you get to sleep after an active day. Since I have been doing some work on dispersion, let's pull up ITU G.695 - Characteristics of Optical Systems. I want to see if the work published in my previous blog posts on dispersion are consistent with what is contained in an industry standard. This will be a fairly brief post, but it will pull together the information from several previous posts. Continue reading

Posted in Fiber Optics | Tagged , , | Leave a comment

## Optical Fiber Dispersion Formula - Where Did This Come From?

Most Fiber-To-The-Home (FTTH) deployments in North America use SMF-28e fiber from Corning, which is to fiber what Kleenex is to tissue. Unfortunately, I am so familiar with this particularly product that I can recite its specifications from memory. However, there is one aspect of SMF-28e's datasheet that I have never really understood – the chromatic dispersion formula shown in Figure 1. This formula is used to determine the fiber parameter D(λ), which specifies the travel time difference (in picoseconds [ps]) for photons that differ by 1 nm in wavelength over 1 km of fiber. Continue reading

Posted in Fiber Optics | 4 Comments

## Customer Service Math

While this post does not address a math problem, it does address an important aspect of mathematics -- the presentation of data. I occasionally have to prepare information on various items for our Customer Service group. For a number of years, I have maintained a graphic that shows the average cost of a kW-hr of energy by state. Our customers use this data to estimate the yearly operating cost of our equipment in their deployments. I get the statistics from the Department of Energy (DoE) Website. It is a hassle to manually update all 50 states and DC, so I use a spreadsheet to link the data I download from the DoE to Visio. It gives me the graphic you see below. I got the original map of North America from the Visguy website. Continue reading

Posted in Management | 12 Comments

## Phone Loads For Backup Time Testing

Introduction I often have to assist with writing test procedures. One of our procedures involves testing the battery backup time for the equipment we install at the subscriber's home, which is called an Optical Network Unit (ONU). Nearly all ONUs … Continue reading

Posted in Electronics | Leave a comment

## Dimensional Analysis and Submarine Running Time

Introduction Part of my job is looking at backup power sources for remote telecommunications gear. I recently have been doing some reading on fuel cells, which we are starting to see in some backup power applications. I started googling to see … Continue reading

Posted in Electronics | 3 Comments

## Battery Self-Discharge Math

Quote of the Day Life isn't about finding yourself. Life is about creating yourself. — George Bernard Shaw:" Introduction I deal with a lot of battery issues. Our products generally ship with an Uninterruptible Power Supply (UPS) that contains a … Continue reading

Posted in Electronics | Tagged , | 8 Comments