# E

### E detector, ΔE detector

The E detector is a detector with a thickness enough to cover the range of high energy particles. It is designed for detecting the total energy of a particle. The ΔE detector in contrast is made thin enough to allow the particles being detected to pass through it so that the specific energy loss in the particle can be detected. A combination of a ΔE detector and E detector is called the ΔE-E detector and is an effective means of identifying particles.

### EDFA (erbium-doped fiber amplifier)

A device that directly amplifies light using a quartz-based optical fiber with an erbium-doped core. Light is amplified in the optical fiber by induced radiation. When a weak light signal enters the EDFA, light amplification occurs at the same wavelength as the signal light. The EDFA is widely used as an optical amplifier for long-distance optical fiber communication in the 1.55 µm band.

### Ethernet

Ethernet is one of several computer network standards. This was devised by Xerox and DEC (currently part of Hewlett Packard) and standardized by the IEEE 802.3 committee. This is the most common LAN (local area network) standard and is widely used in offices and homes all over the world.

### ENI - Photomultiplier tube

ENI indicates the photon-limited signal-to-noise ratio. ENI refers to the amount of light in watts necessary to produce a signal-to-noise ratio of unity in the output of a photomultiplier tube. The value of ENI is given by the equation on the left. $$ENI = \frac{\sqrt{2q \cdot Idb \cdot \mu \cdot \triangle f\ }}{S}(watts)$$ q = electronic charge (1.60 x 10-19 coul.)
Idb = anode dark current in amperes after 30 minute storage in darkness
μ = gain
△f = bandwidth of the system in hertz(usually 1 hertz)
S = anode radiant sensitivity in amperes per watt at the wavelength of interest

### Equivalent background input

This indicates the input illuminance required to produce a luminous emittance from the phosphor screen, equal to that obtained when the input illuminance on the photocathode is zero. This indicates the inherent background level or lower limit of detectable illuminance of an image intensifier.

### eV (electron volt)

Energy acquired by an electron when it is accelerated through a potential difference of 1 V in a vacuum. This is generally used as a unit to express the energy of elementary particles, atomic nuclei, atoms, and molecules, etc.$$1\ eV = 1.602 \cdot 10^{-19} J$$

### Excitation

In semiconductors, excitation refers to the process of raising electrons from a low-energy valence band to the higher-energy conduction band. If electrons are excited by heat, this process is called thermal excitation. If an electron is excited by light, then this process is called photoexcitation. Light absorption by a photodiode is photoexcitation.

### Extinction ratio

The ratio of the minimum value to the maximum value in the light power that varies during intensity modulation of light waves. In digital optical communications, this is defined as the ratio of the light power for transferring logic “1” to the light power for transferring logic “0.” This extinction ratio is expressed in either linear ratio, dB, or %.

[Extinction ratio in digital optical communications]
$$Extinction\ ratio\ (linear\ ratio) = \frac{I(1)}{I(0)}$$ $$Extinction\ ratio\ [dB] = 10\ log^{10}{extinction\ ratio\ (linear\ ratio)}$$ $$Extinction\ ratio\ [％] = \frac{I(0)}{I(1)} \cdot 100$$  I(1): light power for transferring logic “1”
I(0): light power for transferring logic “0”

### Eye diagram

This is a superimposed display of all waveforms for possible encoded strings, used to perform a comprehensive evaluation of the waveform distortion of the transmitted encoded pulses. This is also called the eye pattern.