ECOC 1975 - ECOC 2013

144
A 32 MB/S REGENERATIVE REPEATER FOR FIBRE CABLE TRANSMISSION
J. Yamagata, S. Senmoto, Y. Inamura, H. Kaneko and T. Takahashi
INTRODUCTION
This paper presents an outline and some performance evaluations of a 32
Mb/s regenerative repeater for fibre cable transmission use.
The intermediate repeater was developed as a part of a 4 MHz video
transmission system.
OUTLINE OF THE REPEATER
The b10ckdiagram and the parameters of the 32 Mb/s regenerative repeater
are shown and listed in Figure 1 and Table 1, respectively.
The repeater uses a Si avalanche photodiode (APD) as the photo-detector and
a GaA1As laser diode as the optical source.
APD bias voltage is supplied by an internal DC-DC converter which converts
external low d.c. voltage to stable high d.c. voltage.
The preamplifier uses bipolar transistors and has the input impedance of
600 ohms for frequencies less than 30 MHz.
The main amplifier has the reshaping function in addition to amplification.
The peak level of the pulse at the decision point is kept constant by
an AGC whose control range is greater than 40 dB.
A monolithic crystal filter is used as the timing extractor (TIM EXT) ,
because of its high Q and small dimension.
The d.c. restoration circuit (DC RES) is employed in order to compensate
d.c. wander which is caused by a.c. coupling at the amplifiers.
The regenerated pulse enters into the driver(DRIV) which directry modulates
the laser diode. Output light beams from the laser diode are emitted
in two directions, forward and backward. The forward beam is the optical
output carrier. The backward one is monitored by a p-i-n photodiode and
fed back to the driver through a peak detector (PD). By this loop, called
automatic power control loop, the laser diode output power is stabilized.
Figure 2 is a photograph of the repeater. The dimensions of the repeater
are 90 x 50 x 197 rom. The total power consumption is about 3.6 watts.
EXPERIMENTAL RESULTS
Figures 3 and 4 show the error rate and the sinusoidal crosstalk margin
characteristics as a function of the average optical receiving power
for pseudo-random code, respectively.
In the measurement, a graded index fibre with 22 dB/km loss was used.
Each piese of the fibre cable was 200 m in length, and jointed together (
1400 m maximum) by fibre connectors when necessary.
Figure 3 indicates that the pulse dispersion is almost negligible
within such fibre length as 1400 ro, and that the average optical receiving
power necessary for a 10- 9 error rate is approximately -53 dBm.
J. Yamagata, S. Senmoto and Y. Inamura are with Nippon Telegraph and
Telephone Public Corporation.
H. Kaneko and T. Takahashi are with Nippon Electric Company, Ltd.