EP0102815A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Optical communication
Assignee: British Telecommunications PLC
•
Filing: 1983-08-25
•
Granted: —
•
Expires: 2003-08-25
Abstract
Abstract An optical communication system using digital pulse position modulation employs a mode locked laser with a mode locking frequency equal to the time slot frequency of the modulation and means dependent on groups of cosecu- tive digits of the data to be transmitted to select pulses from the laser for transmission. In one example, 4-bit groups from the data for transmission select one out of 20 pulses from the laser thus leaving a guard interval of 4 time slot periods between position modulated pulses.An encoder and a decoder for converting between digitally encoded data and position modulated pulses are described. These use a counter driven by clock pulses at the time slot frequency to supply inputs alternately to two encoding logic circuits or two multiplexers.
Inventors
- 👤 Ian Garrett
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-04 21:54
CPC Classifications
H; H04; H04J; H04J3/00; H04J3/16; H04J3/1676; H01; H01S; H01S3/00; H01S3/10; H04B; H04B10/00; H04B10/60; H04B10/66; H04B10/69; H04B10/697; H04B10/6972; H04B14/00; H04B14/02; H04B14/026
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
82 words
Transmission apparatus for an optical communication system using digital pulse position modulation in which each pulse is in one of a plurality of time slots and represents a group of digits of input data, wherein the optical pulses are generated by a mode locked laser with a mode locking frequency equal to the time slot frequency of the modulation, and optical pulses from the laser are selected and coupled for transmission in dependence upon consecutive groups of digits of the input data.
Claim 2
Dependent Claim
82 words
Transmission apparatus for an optical communication system using digital pulse position modulation in which each pulse is in one of a plurality of time slots and represents a group of digits of input data, wherein the optical pulses are generated by a mode locked laser with a mode locking frequency equal to the time slot frequency of the modulation, and optical pulses from the laser are selected and coupled for transmission in dependence upon consecutive groups of digits of the input data.
Claim 3
Dependent Claim
78 words
Apparatus according to claim 1, including means for storing a group of digits of the input data, means responsive to the stored group of digits for producing a position modulated pulse occurring at a time instant within a time interval, which instant represents the stored group of digits, and means responsive to the position modulated pulse for selecting and coupling for transmission a corresponding one of the optical pulses generated during the interval by the mode locked laser.
Claim 4
Dependent Claim
34 words
Apparatus according to claim 2 wherein the input data is in binary coded form, a group of digits contains n digits and there are 2 n possible time positions for the position modulated pulse.
Claim 5
Dependent Claim
9 words
Apparatus according tc claim 3 wherein n is 4.
Claim 6
Dependent Claim
58 words
Apparatus according to claim 3 or 4 wherein the time interval is longer than the minimum necessary to accommodate the 2 n possible time positions, so that there is a time period longer than that between adjacent time positions between the latest possible time position in one interval and the earliest possible time position in the next interval.
Claim 7
Dependent Claim
23 words
Apparatus according to claim 5 when dependent on claim 4, wherein the time interval is of a length to accommodate 20 time positions.
Claim 8
Dependent Claim
40 words
Apparatus according to any of claims 3 to 6 wherein the input data is in serial coded form and the repetition frequency of the digits of the input data is an integral multiple of the reciprocal of the time interval.
Claim 9
Dependent Claim
30 words
Apparatus according to any of claims 2 to 7 in which the means for selecting and coupling for transmission of the optical pulses from the laser includes a cavity dumper.
Claim 10
Dependent Claim
146 words
Conversion means for converting digital data between a first form comprising position modulated pulses occurring in particular time slots representing by the time slots in which they occur respective groups of digits and a second form comprising the groups of digits, the means including a clock pulse generator generating clock pulses at the time slot frequency, counting means having at least as many stages as there are digits in a group and counting in the same radix as the digits, means for causing the counting means to count clock pulses from a datum time until the time of occurrence of a position modulated pulse when the counting means records the groups of digits corresponding to the time position of the pulse, and means for deriving output data in one form from input data in the other form in response to the state of the counting means.
Claim 11
Dependent Claim
146 words
Conversion means for converting digital data between a first form comprising position modulated pulses occurring in particular time slots representing by the time slots in which they occur respective groups of digits and a second form comprising the groups of digits, the means including a clock pulse generator generating clock pulses at the time slot frequency, counting means having at least as many stages as there are digits in a group and counting in the same radix as the digits, means for causing the counting means to count clock pulses from a datum time until the time of occurrence of a position modulated pulse when the counting means records the groups of digits corresponding to the time position of the pulse, and means for deriving output data in one form from input data in the other form in response to the state of the counting means.
Claim 12
Dependent Claim
150 words
Conversion means according to claim 9 for converting groups of digits of input data into position modulated pulses occurring in particular time slots representing respective digit groups, the means including storage means for a group of digits of the input data, counter means having at least as many stages as there are digits in a group and counting in the same radix as the digits of the input data, a source of clock pulses at the time slot frequency, a plurality of digit comparison circuits respectively connected to compare digits of the group stored in the storage means with corresponding digit stages of the counter means, and logic means connected to the outputs of the digit comparison circuits and arranged to produce an output pulse when digits stored in the stages of the counter means are the same as the respective digits of the group stored in the storage means.
Claim 13
Dependent Claim
94 words
Conversion means according to claim 10 including two or more storage means, means for applying groups of digits of input data to the storage means for storage therein in sequence, two or more pluralities of digit comparison circuits connected to compare respective digit groups stored in the two or more storage means with the state of the counter means, whereby one storage means may be arranged to receive a group of digits for storage whilst the group of digits stored in another storage means is being compared with the state of the counting means.
Claim 14
Dependent Claim
20 words
Conversion means according to claim 11 wherein the digits of the input data are applied serially to the storage means.
Claim 15
Dependent Claim
80 words
Conversion means according to any of claims 10 to 12 wherein the time slot frequency is sufficiently high in relation to the repetition rate of the groups of digits of the input data that the counter. means can assume all possible combinations of digits in a group of digits within a period cf time which is significantly less than the time interval from the start of one group of digits to the start of the next in the input data.
Claim 16
Dependent Claim
84 words
Conversion means according to claim 13 wherein the input data is in binary code, the counter means counts in the scale of 2, there are four digits in a group of digits, and the time slot frequency is 20 times the repetition rate of the groups of digits in the input data, whereby the time period between the latest possible output pulse representing one group of digits and the earliest possible output pulse representing the next group of digits is five time slot periods.
Claim 17
Dependent Claim
31 words
Apparatus according to claim 2 wherein the means responsive to the stored group of digits producing a position modulated pulse includes conversion means according to any of claims 9 to 14.
Claim 18
Dependent Claim
99 words
Conversion means according to claim 9 for converting position modulated pulses occurring in particular time slots representing respective groups of digits into the corresponding groups of digits, the means including a clock pulse generator generating clock pulses at the time slot frequency, counting means counting in the same radix as the digits and connected to count the clock pulses, means for resetting the counting means to a predetermined initial value at datum times, and means for reading groups of digits recorded by the counting means whan a position modulated pulse occurs and producing the group of digits as output.
Claim 19
Dependent Claim
30 words
Conversion means according to claim 16 wherein the group of digits recorded by the counting means when the position modulated pulse occurs is transferred in parallel to a storage means.
Claim 20
Dependent Claim
35 words
Conversion means according to claim 17 wherein there are provided two storage means to which the groups of digits are transferred alternately and from which the digits of the groups are produced as output serially.
Claim 21
Dependent Claim
54 words
, 19 Conversion means according to claim 18 wherein the counting means counts in the scale of two, the groups of digits are in binary code, there are four digits in a group of digits, and the time slot frequency is 20 times the repetition frequency of the groups of digits forming the output.
Claim 22
Independent Claim
159 words
A method of transmitting digital data including deriving from groups of the digits of the data position modulated electrical pulses respectively representing the groups of digits by counting clock pulses at a time slot frequency until the count has a specific relationship to the group of digits and then generating the position modulated electrical pulse, producing a succession of pulses of optical energy at the time slot frequency from a mode locked laser, selecting and coupling for transmission optical energy pulses from the succession in response to the position modulated pulses, receiving the transmitted optical energy pulses and deriving from them position modulated electrical pulses, converting each position modulated electrical pulse into a corresponding group of.digits by counting clock pulses at the time slot frequency for the time interval between a datum time and the occurrence of the electrical pulse and using the count reached to generate the group of digits, and producing as output the groups of digits.
Claim 23
Independent Claim
159 words
A method of transmitting digital data including deriving from groups of the digits of the data position modulated electrical pulses respectively representing the groups of digits by counting clock pulses at a time slot frequency until the count has a specific relationship to the group of digits and then generating the position modulated electrical pulse, producing a succession of pulses of optical energy at the time slot frequency from a mode locked laser, selecting and coupling for transmission optical energy pulses from the succession in response to the position modulated pulses, receiving the transmitted optical energy pulses and deriving from them position modulated electrical pulses, converting each position modulated electrical pulse into a corresponding group of.digits by counting clock pulses at the time slot frequency for the time interval between a datum time and the occurrence of the electrical pulse and using the count reached to generate the group of digits, and producing as output the groups of digits.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.