Attenuators

The first tool we'll look at is a simple attenuator.  It's like a resistor for signals.  You put so much signal in, and you get less out.  Here's a picture of an RF attenuator.  And you can buy this optical attenuator on Amazon.

Attenuators are most important because many tools (like spectrum analyzers or protocol analyzers) require very little input power, and if they get too much, you can overpower them and let out the "magic smoke."  Attenuators are used to drop the power sent to the equipment so that it's not damaged.

RF attenuators are usually big and bulky because they have to deal with large amounts of power.  It's not atypical to have some that are about six inches long and two inches wide to handle 50 watts.  I once had to handle several of those with oven gloves!  They can easily burn you if you don't treat them with respect.

Optical attenuators can be much smaller, because the power involved is typically on the order of nanowatts.  You can think of them as "sunglasses" for the fiber-optic line.

Attenuators are measured in "dB" or decibels.  A rule of thumb is that 3 dB attenuates the signal to about half its power, and 10 dB brings it down to one tenth its power.

Picture linked is courtesy of Joe Ravi, CC-BY-SA 3.0.