
52-6 Optical
52.3.1 Light Interference
Most optical spectrum analyzers make measurements utilizing light interference. e wave theory of
li
ght
ca
n
ex
plain
in
terference
. A sin
gle-mode,
na
rrow-linewidth
la
ser
be
am
ca
n
be de
scribed
by it
s
el
ectric
eld
E(z)
:
E z A i z i t( ) [ ( ) ( )]= − +exp
φ α
(52.2)
where
A
i
s
t
he
a
mplitude
ϕ(z)
= 2πz/λ is th
e
ph
ase,
λ is th
e
la
ser
wa
velength,
z is th
e
co
ordinate
in th
e
di
rection
of be
am
propagation
α(t)
i
s
a p
hase
f
actor
t
hat
v
aries
f
ast
w
ith
t
ime
t
e
i
ntensity
o
f
t
he
l
aser
b
eam
i
s
g
iven
b
y
I E z A= =| ( )|
2 2
(5
2
.3)
5
2.3.1.1
T
wo
-Beam Interference
A
b
eam
s
plitter
s
uch
a
s
a p
artially
t
ransparent
p
late
c
an
s
plit ...