Error detection/correction and fault detection/recovery – Pulse or data error handling – Transmission facility testing
Reexamination Certificate
2000-11-01
2003-08-26
Chung, Phung M. (Department: 2133)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Transmission facility testing
C714S738000
Reexamination Certificate
active
06611928
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a homo-code (identical or same code) continuity proof testing device, and in particular to a homo-code continuity proof testing device which conducts tests with test data including a predetermined homo-code continuity proof test pattern.
In recent years, a digital network has become rapidly widespread with the advance of an LSI technique, an optical fiber cable technique, a digital signal processing technique, and the like. For transferring a signal from a transmitting device to a receiving device in an asynchronous state in the digital network, there is a method wherein the receiving device extracts a clock included in a received signal to perform the receiving operation for the signal in synchronization with the extracted clock.
When the received signal includes a continuous or sequential homo-code in this method, it is difficult for the receiving device to extract the clock. As a measure for this difficulty, the transmitting device scrambles and transmits the signal so as not to include the continuous homo-code, while the receiving device extracts the clock from the received signal and then descrambles the received signal to restore the signal before the scrambling.
However, there is a possibility that the continuous homo-code is included even in the scrambled signal. Therefore, it is important how many bits continued with a homo-code at maximum would enable the receiving device to accurately extract the clock from the signal, that is whether or not the receiving device has a homo-code continuity proof strength.
2. Description of the Related Art
FIG. 16
shows an arrangement of a prior art homo-code continuity proof testing device
10
. A device
40
to be tested is connected to the testing device
10
with a transmission line
30
which transmits a signal
100
. In this arrangement, the transmission line
30
is an optical fiber, and the signal
100
is included in a frame, a packet, a cell, or the like and transmitted through the transmission line
30
.
The testing device
10
is composed of a homo-code continuity pattern inserter
19
which inserts data
105
for generating a homo-code continuity proof test pattern on the transmission line
30
, a frame head timing generator
29
! which generates a frame head timing signal
107
indicating a frame head, a scrambler
16
which scrambles the data
105
from the inserter
19
to generate frame data
106
including a frame head pattern and the homo-code continuity proof test pattern by the timing signal
107
, and an E/O converter
17
which synchronizes (multiplexes) the data
106
with a clock
101
and converts the electrical signal into the optical signal
100
to be transmitted to the transmission line
30
.
The tested device
40
is composed of an O/E converter
41
for outputting data
201
which is the optical signal
100
from the transmission line
30
converted into the electrical signal and for extracting a clock
200
from the signal
100
, a clock disconnection detector
50
for detecting whether or not the extracted clock
200
is disconnected to output a determination result signal
216
, a frame head detector
51
for detecting the head of the frame data
201
to output a frame head timing signal
219
, and a descrambler
42
for descrambling the data
201
to be restored, by the timing of the timing signal
219
being made a starting phase.
As mentioned above, when the homo-code either “0” or “1” continues in the data
100
on the transmission line
30
, the clock components in the data
100
disappear, so that the clock
200
can not be extracted from the tested device
40
. Therefore, the homo-code continuity proof test is performed in order to determine the limit of the homo-code continuity proof strength of the tested device
40
on the receiving side.
Namely, it is tested how many bits continued with the homo-code on the transmission line
30
would disable a clock extractor (not shown) of the O/E converter
41
to extract the clock, and disable the data to be normally received. The maximum bit number at which the clock can be extracted is supposed to be the homo-code continuity proof strength of the tested device
40
.
The operations of the prior art homo-code continuity proof testing device
10
and the tested device
40
will now be described.
The testing device
10
predicts a scramble pattern at the homo-code continuity pattern inserter
19
in order to generate the homo-code continuity proof test pattern on the transmission line
30
, and inserts thereinto such a pattern as the output of the scrambler
16
becomes all “0” or all “1” of a predetermined bit number.
Namely, the scrambler
16
is composed of a shift register and an EXOR circuit (not shown), and a self-reset type of scrambler for resetting a frame to all “1” at the frame head and performing the scrambling per each frame. Accordingly, the scramble pattern of the scrambler
16
can be predicted based on the same generation polynomial, the same starting phase, and the same initial value as the scrambler
16
.
In order to transmit the homo-code of all “0” to the transmission line
30
, the inserter
19
has only to generate the same pattern as the one at the scrambling time, and has only to provide the scrambler
16
with the pattern data
105
generated by the same generation polynomial, starting phase, and initial value as the scrambler
16
.
Similarly, in order to transmit the homo-code of all “1” to the transmission line
30
, the inserter
19
has only to provide the scrambler
16
with the inverted pattern data
105
of the scramble pattern.
It is to be noted that a frame head detecting pattern is mapped at the head of the frame, so that the scrambler
16
detects the head position by the timing signal
107
and scrambles all of the bits except the frame head detecting pattern.
The reason why the frame head detecting pattern is excluded from the scramble object is that the tested device
40
establishes a frame synchronization by this pattern.
The E/O converter
17
synchronizes (multiplexes) the data
106
with the clock
101
, and converts the data
106
from the electrical signal into the optical signal
100
to be outputted to the transmission line
30
.
In the tested device
40
, the O/E converter
41
converts the received optical signal
100
into the electrical signal to extract the data
201
and the clock
200
. The clock disconnection detector
50
determines the result of the homo-code continuity proof test by monitoring the clock disconnection. That the clock has been normally extracted means that the device has a strength for the homo-code continuity proof test pattern, while that the clock disconnection has been detected means that the device does not have a strength for the homo-code continuity proof test pattern.
In addition, the frame head detector
51
detects the frame head by the frame head detecting pattern, and the descrambler
42
restores the receiving data by starting the descrambling from the bit next to the frame head detecting pattern.
Thus, the prior art homo-code continuity proof testing device has determined the homo-code continuity proof strength by detecting the clock disconnection.
In such a determination method by the prior art homo-code continuity proof test, the determination reference is vague to what degree of disturbance of the extracted clock
200
the clock disconnection detector
50
can determine the clock disconnection, so that the disturbance of the extracted clock
200
influences the determination result. Therefore, there is a problem that the homo-code continuity proof strength can not be determined with a high accuracy.
On the other hand, the homo-code continuity proof testing device of the ATM-PON (Asynchronous Transfer Mode Passive Optical Network) system conformed to the ITU-T recommendation G.983 has also a problem, which will now be described.
The technique of the ATM-PON system is indispensable for the construction of such an optical access network as represented by the FTTH (Fiber to
Abiru Setsuo
Fujiyoshi Shinichi
Hirashima Katsuhiko
Koyanagi Toshinori
Ryu Kazuya
Chung Phung M.
Katten Muchin Zavis & Rosenman
LandOfFree
Homo-code continuity proof testing device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Homo-code continuity proof testing device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Homo-code continuity proof testing device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3116616