Note: Descriptions are shown in the official language in which they were submitted.
2~8~1S
The present invention relates to test equipment
for manually testing an optical glassfibre subscriber line.
The employment of wavelength multiplex operated
glassfibre communication lines in the region of subscriber
stations requires increasingly complicated measuring- and
checking technology to detect the precise function of each
communication line.
Therefore, maintenance staff should be able
to obtain go-no go information with simple means for
monitor~ing the operational readiness of the optical trans-
mission lines and the wavelengths to be transmitted over
the lines.
It is accordingly an object of the present
invention to provide an equipment which, with simple means,
enables monitoring of the operability of communication lines
corresponding to each of the transmitted wavelengths on an
optical subscriber circuit which is operated by wavelength
multiplexing.
The present invention provides test equipment
for manually testing an optical glassfibre subscriber line
which is operated with bidirectional wavelength multiplexing,
the subscriber line being provided in series with: a high
frequency transmitter comprising a parallel/series converter;
an electro-optical converter comprising a laser transmitter;
an opto-electrical converter and a high frequency receiver
comprising a serial/parallel converter, wherein the equip-
ment further comprising key means, including interlocking
means for permitting actuation of the laser transmitter only
during service-free periods, for enabling the laser
~$
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transmitter and permitting the transmission of a period
synchronizàtion signal at one end of the subscriber line;
the high frequency transmitter comprising means for providing
the synchronization signal; means at the opposite end of the
subscriber line for detecting the synchronization signal
after conversion thereof by the opto-electrical converter
and, in response, thereto, generating a logic signal and
transmitting the logic signal in a rearward direction in a
channel of a multi-channel system.
~ Testing the functioning of each individual
transmission line, allocated to respective optical wave-
length, is carried out during the duration of depression of
a corresponding key (at the transmitter station) and is
finished upon the release of the key.
Preferably, the interlocking means test equip-
ment as claimed in Claim 1, wherein the interlocking means
comprise means responsive to a threshold current of the
laser transmitter for enabling the operation of the laser
transmitter.
The equipment may include LED test equipment as
claimed in Claim 1, further comprising ~ED means for indicat-
ing the emission of a TEST signal and the existence of the
logic signal.
An embodiment of the invention is described by
way of example below with reference to the accompanying
drawings in which:-
Figure 1 shows a switching device for a laser
transmitter,
_ 3 _ 1 2~ 5
Eigure 2 shows devices at a remote location of
a transmission path for connecting DSE-signals into a multi-
channel system,
Figure 3 shows the complete equipments at the
starting point and the end point of the transmission path.
In Figure 1 logic signals obtained in depend-
ence of the operational state of a laser transmitter 1 and
more particularly in dependence on the threshold current of
the laser, and by the actuation of a keyboard 2 are combined
10: by an RS-flipflop (not shown). As a result of the combina-
tion, a "TEST" logic signal is produced. The circuit for
generating the "TEST" logic signal includes an "OR"-output
so that the simulation of the function of the keyboard 2
by other sources is also possible.
The function of the keyboard 2 is overridden
as long as the laser transmitter 1 is in operation, i.e. the
threshold current is flowing.
The initiation of the manuel subscriber line
test is displayed at the laser transmitter to be tested by
a LED (not shown).
As shown in Figure l a cable is used to trans-
mit data signals D and bit time signals BT on lines 4 and 5
between a high frequency transmitter 7 and a corresponding
electro-optical converter, i.e. the laser transmitter 1, as
is well known in the art. A line 6 is used for transmitting
back the "TEST" logic signal and carries out the following
two functions, with self-holding of the high frequency trans-
mitter 7 during the keyboard operation:
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a) switching on the high frequency transmitter
7 through an input e~a,
b) generation of a continuous synchronization
signal, which is initiated by an input DS. The output of
data signals is blocked as long as the continuous synchroni-
zation signal is generated. Transmission of the continuous
synchronization signal means that the whole time-multiplex-
frame which is generated in the high frequency transmitter 7
is occupied by a synchronizing word at each time point.
~ Figure 2 shows by way of example an embodiment
of a circuit for wavelengths ~1 and ~4.
At the remote end of the transmission line for
the wavelength ~1 the continuous synchronization signals
for the wavelength ~1 are detected. Additionally a converter
10 carries out an opto-electrical conversion. From the out-
put signal of the converter 10 the seriall~ transmitted data
D and the accompanying bit timing signal BT, which is
generated by means of a phase-locked loop-circuit (not shown)
are supplied to a serial-parallel-converter, which comprises
a high frequency receiver 11 together with means for corres-
ponding time frame- and continuous synchronization identi-
fication. As a result of the identification of the con-
tinuous synchronization signal, a "DSE" logic signal is
generated.
The output of the circuit generating the "DSE"
logic signal is provided with an OR gate so that "DSE"-
signals from a plurality of transmission lines, operated at
different wavelengths (e.g. ~2'~3)' can be summarized at a
junction point 8.
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The "DSE" logic signal is supplied to a stand-
by circuit 9 which is allocated to the line for wavelength
~4. Upon application of the "DSE"-signal the high frequency
transmitter 7 is switched on by output e/a of the stand-by
circuit 9. In this state the high frequency transmitter 7
generates a time-multiplex-frame beginning with a synchroniz-
ing block. A PCM multi-channel system (in this embodiment a
PCM system with 30 channels (PCM 30)) is connected by the
stand-by circuit 9 through a multiplex device 13 in this
time-multiplex-frame. For the time duration o~ the test the
stand-by circuit 9 supplies the "DSE"-signal to an 8 kbit/s-
channel of the PCM-30 system which is reserved for the "DSE"
-transmission. The serially data stream D supplied by the
high frequency transmitter 7, which includes the "DSE"-signal,
is passed together with the bit timing signal BT to the
electro-optical converter 1, i.e. the laser transmitter.
The test ("forward test") can also be initiated
directly at the electro-optical converter 1 in the above
described -nn~r by the key 2, which is allocated to the
laser transmitter 1. If the test is initiated by the key
2, the time frame which is transmitted on the transmission
line with the wavelength ~4 is filled uninterruptedly with
synchronizing words.
As it is shown in Figure 3 the backwardly trans-
mitted data are received by an electro-optical converter lOa
and further processed in serial/parallel-converter 11. If a
tr~n~m;tted data includes the "DSE"-signal in a 8 kbit/s-
channel of a PCM-30-system the "DSE"-signal is detected by
multiplex devices 13 and 14 and displayed by a LED 3a. If
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otherwise the received information consists of synchronizing
words the "DSE"-signal is directly detected in the serial/
parallel-converter ll and also can be displayed by a LED.
Figure 3 shows further that the "DSE"-signal
also can be fed in an 8 kbit/s-channel of a PC~-30-system
which is transmitted thereupon by the electro-optical con-
verter l (laser transmitter) with the wavelength ~l For
this purpose the stand-by circuit 9, the multiplexer 13
~format converter 13) and the high frequency transmitter
HF-S 7 iare employed as described with reference to Figure 2.
The invention offers the possibility for a
simple test of the functions of the essential parts of a
transmission line.
Thereby the transmission of data consisting
of synchronization words is effected at the transmitting
station by a keyboard and an interlocking device which en-
ables the laser transmitter only during a time which is
free of services. At the remote location of the transmission
line this data is detected and outputted as the "DSE" logic
2~ signal and eventually is displayed by a LED.
By means of the stand-by circuit 9 the "DSE"
~signal can be transmitted back to the location at which
the test is initiated by a further wavelength in a reserved
channel of the multi-channel system.
