We live in a world that is increasingly different from the one in which our ancestors received their genetic programming. Today, our minds constantly use abstractions to negotiate our way through the world.
An example of this is the process we use to steer an automobile.
(A fun fact to know is that when automobiles were first introduced, there was great debate on how to steer them. Some early cars had reins similar to horses, others had a tiller like small sailing boats, and still others used a wheel like those found on larger ships.)
Fun facts aside, when you drive a car today with a steering wheel, you are using a solid object to perform an abstraction, all within the blink of an eye. When you turn the steering wheel, you are not only turning the wheel, you are turning the wheels of the car and guiding the car in the direction you wish to go. The small movements you make are amplified and strengthened through a power steering mechanism and then onto some rack and pinion structure to move the wheels that contact the road and keep the vehicle on the right track.
Nevertheless, your mind translates all of this for you so that you can turn the wheel in various motions and you don’t really have to think about the concrete business of guiding the car. Your mind abstracts the motion of the steering wheel into the motion of the car.
Now you might be asking yourself: “Where are we going with all this? What does this have to do with Finisar primary focus in designing, manufacturing and marketing the best possible optical subsystems?”
It is true that Finisar designs, manufactures and markets optical subsystems, and we do that by working in abstractions. Abstractions are really just constructs of our minds, despite the fact that we often accept them as reality and don’t question them sufficiently.
Let me describe how we at Finisar use abstractions as tools, and present some arguments on why we should test and validate common abstracts more carefully.
How One Abstraction Begets Another
Finisar’s optical subsystems include optical transmitters/receivers (or transceivers) that either transform electrical signals into optical signals (transmitters) or optical signals into electrical currents (receivers). These devices are usually digital in nature and operate at speeds above one billion bits per second or one Gigabit per second (Gb/s).
We observe these optical or electrical signals using a device called an oscilloscope. An oscilloscope produces an image on a screen that looks like this:
The picture above is what we call an “eye diagram,” which is simply a picture of the bits that are sent on the fiber optic glass strand. In this picture, you see the results of many different bits each overlaid on top of one another.
How this picture is interpreted and how we use it represents the crux of what Finisar does and why Finisar’s products are known to produce some of the very best eye diagrams in the world.
Measuring the Eye
The figure below shows how we create the eye pattern. Imagine an idealized string of bits comprised in a 1 – 0 – 1 pattern (the first diagram in the figure).
In an optical fiber, a laser emits a bright light to represent a â€˜1′ and sends no light (the fiber is dark) for a â€˜0.’ Within the fiber the light turns on and off to form the sequence of 1, 0, 1, and so on. The laser cannot turn on and off instantaneously, so there are some instants in time where the light is growing brighter or fainter as it goes on or off. This is the transition point between a 0 to a 1 or from a 1 to a 0.
If we use the oscilloscope with a careful “trigger,” we can see what these bits look like, which is shown in the third diagram in the figure above. Here we see the oscilloscope trying to “trace” out the bit to measure the light as it emerges from the fiber.
If we use the oscilloscope to look at the light emerging from the fiber over many bits and if the bits are coming out are random, we sometimes will overlay 1s on top of 0s and vice-versa. When this happens we get an eye pattern, shown in the fourth diagram of the figure above. Notice that this diagram is just like the one above it with the pattern sometimes inverted.
Look again at the LCD oscilloscope eye pattern (below) and you will see how this really looks to us as we measure a Finisar transceiver.
Abstractions As Building Blocks
Here’s a step by step description of how we link abstractions together to create the eye patterns in an oscilloscope:
- The end of the fiber is connected to a photodiode that converts the light to a current of electricity.
- This current is transformed to a voltage by means of a transimpedance amplifier.
- The amplifier provides gain whereby the signal level is increased typically by more than a factor of 1,000.
- The output of the amplifier is presented to the oscilloscope which “samples” the voltage periodically. The voltage is turned into a number by means of an analog to digital converter.
- An internal clock in the oscilloscope determines how often the voltage is sampled.
- As the samples are digitized, the output is fed into computer memory for storage.
- A computer takes the data out of memory and displays it on the LCD display screen.
- Data taken at different times and voltages is painted across the screen one dot at a time. Thousands of dots are required to make an eye pattern.
- Data is typically taken from one point every few hundred bits. This means that the actual data on the eye pattern represents single dots per bit taken every few hundred bits. Thus, the data is taken over millions and billion of bits.
This is pretty confusing, but the point here is every step must be precisely correct. The eye pattern will be severely distorted if any of the following problems occur:
- The end of the fiber is not well connected to the photodiode so that some of the light is lost by not hitting the photodiode.
- The photodiode transforms the light from the fiber into a current but does not do this linearly so the light represented by the current is inaccurate.
- The amplifier gain varies over time, temperature or something else or is not linear so that the gain of 1000 is sometimes 900 or 1500.
- The analog to digital converter is inaccurate.
- The clock in the oscilloscope is inaccurate.
- The samples are not stored properly in the computer memory.
- The software in the computer is not programmed correctly.
The changing of the light from faint to bright or the reverse takes about 100 trillionths of a second. It’s extremely fast. No â€˜blinks of an eye’ or other analogies will work here. It is just plain fast, faster than anyone can possibly imagine.
You get the idea. Every abstraction we make introduces a potential source of error. If any one of these is wrong it is difficult to determine which one it is.
More Fun with Abstractions
So now you say, “How does this affect me”? I don’t create eye patterns on my job and driving a car doesn’t seem so abstract when I’m actually in the car.
There are other abstractions everywhere. Here are some fun historical ones for you to think about:
- Around 1500 it was determined by Copernicus, Galileo and Columbus that the earth was a sphere and that it orbited about the sun (though there was some discomfort on this for most involved). Did you know that it took another 400 years for us to guess that our sun was NOT at the center of the universe? (This happened in the early 1900s when we observed certain globular star clusters and found that they orbited some 50,000 light years distant from us in the center of our Milky Way Galaxy.) We could not easily break free from our abstraction that mankind was the center of creation.
- In both the old and new testaments of the Bible it is written that human generation occurs when a man plants his seed in a woman. Putting in modern terms, the ancients thought that men were entirely responsible for generation, and women were the “dirt” into which the seed was sown. Perhaps this explains why men were dominant in many cultures for thousands of years (Even today we still speak of men sowing their wild oats). We were stuck in an abstraction that affected much of how men and women related to each other. Today we know that men and women both contribute genetic material to create new little human beings. This corrected abstraction undoubtedly helps us have a more equal partnership between men and women.
- During the energy crisis of the 1970s, we abstracted our energy supply such that many were convinced that we would “run out” very soon. That did not happen, and within a few years the world was again awash in oil. Now we are trying to understand global warming and greenhouse gases. There are abundant abstractions in this area, and we do not understand them very well at all.
- For a long time, computers, memories, disks and such were sized for their expected usages. To overbuild a computer was really expensive. Over time, components like memory have dropped vastly in cost, but it took time for us to understand that the potential uses for memory were virtually unlimited. Early PCs could only support 640K of memory. Such hardware limitations were specifically designed into even the Microsoft software architecture, and we allowed this abstraction to limit us for several years.
Using Abstractions to Foster Innovation and Success
Sometimes we embellish our view of the world by creating abstractions that have a worth that is not real. Other times, unimaginative abstractions limit our ability to invent or progress as a society.
Abstractions are everywhere because they are the tools that humans use to form mental images of their changing and evolving world. They are products of our minds, whether we are driving a car, trying to understand human conception or trying to measure the transmission of light as it travels down an optical fiber.
Today, because of the complexity of our world, most abstractions come in layers, and the failure of any one layer can alter your view of what really is there. Be aware of the abstractions you accept. When something seems not to fit or work, look where you have abstracted the world from what reality is there physically. Then go look at each abstraction between what is wrong and what is reality. It is such investigation and questioning the moves us forward.
(Original essay published in September, 2001 when at Finisar)
Posted in Optical Technology, Spiritual Threads