Тable 2
Parameters of the system in comparison with IFOG
Element
Conventional IFOG
The setup
1.3
μ
m SLD
Output power
>
200
μ
W Output power
>
600
μ
W
SSR (or coil)
Length 500–1000m
Length
<
200
m
Beam splitter (50 : 50) Extinction ratio
>
20
dB The same
Insertion loss
<
0
.
2
dB
MIOC Splitting ratio
Insertion loss
<
3
dB
The same
(49.6/50.4)
Extinction ratio
>
40
dB
Bandwidth 500 MHz
Coupler A (90 : 10)
No need
Extinction ratio
>
20
dB
Insertion loss
<
0
.
2
dB
η
D
, P
in
are the efficiency of PD and the power of the SLD, respectively;
T
(
φ
s
) = 4
p
+2
q
M
m
=1
η
2
m
[1 + cos(2
mφ
s
)]
is the light transmission coefficient
inside the SSR;
S
(
φ
s
) =
dT
(
φ
s
)
d
(
φ
s
)
is the scale factor.
In the system configuration with passive SSR, the resolution of the
system depends significantly on the power coupling ratio of coupler A. In
order to ensure the maximum SF and the best resolution, the coupling ratio
(90 : 10) should be selected.
Development of the super luminescent diode.
For the proposed MOG
system, a superluminescent diode (SLD) with the output power of 0.6–
1.0 mW is required. Suppose the coupling efficiency between the SLD chip
and the PM fiber pigtail is around 30%, the output power of the SLD chip
should be higher than 3 mW at the injection current of 100 mA and the
temperature of
20
◦
C.
To realize the SLD, low optical loss, high internal quantum efficiency,
and high gain are the three key features for the epitaxial layers. The epitaxial
structures for the emission wavelength at 1300 nm were grown by metal
organic chemical vapor deposition (MOCVD) on
S
doped
n
-type (100)-
eriented InP substrate. All the layers were lattice-matched to the InP wafer
except for the QWs, which were grown with a compressive strain.
We have designed and fabricated three epitaxial layers with different
structures, doping profile in p-cladding layers, and the number of QWs.
Finally, we selected the structure, which contains eight QWs. In the
structure, a graded-refractive-index separate confinement heterostructure
(GRIN-SCH) is used for realizing four energy steps from 1.1 to 1.3 eV with
ISSN 0236-3933. Вестник МГТУ им. Н.Э. Баумана. Сер. “Приборостроение”. 2005. № 4 111
