METHOD AND DEVICE FOR MEASURING A PULSE SIGNAL WITH HIGH DYNAMIC RANGE

Abstract

The invention relates to devices and methods of characterising a single unknown pulse signal. They create multiple replica of the original that may be more reliably measured, by dividing the signal through nodes and using different signal pathways that may apply a temporal delay. The device and methods have multiple fields of application, most notably with the internal confinement fusion industry.

Claims

1. A passive pulse replication device for converting a single uncharacterised pulse signal into a chain of replica pulse signals, of which at least one will be within a predetermined amplitude threshold range comprising: an input node for receiving an incident pulse signal arranged to divide the incident pulse signal between a first and a second signal pathway; the first signal pathway configured to apply a first temporal delay with respect to the second signal pathway; an output node arranged to, combine the pulse signals from the first and the second signal pathway into a single signal pulse train, wherein the input node is configured to divide the pulse signal along the first and the second signal pathways so that the amplitude characteristics of the pulse signal passing along the first signal pathway are different to the amplitude characteristics of the pulse signal passing along the second signal pathway such that the output node receives temporally separated pulse signals of increasing intensity.

2. A device according to claim 1 comprising at least one intermediate node arranged to intersect the first and second signal pathway and divide the pulse signals and; the first or the second signal pathway is configured to apply at least a second temporal delay.

3. A device according to claim 2, wherein the at least one intermediate node is configured to further divide the pulse signal so that the amplitude characteristics of the pulse signals passing along the first signal pathway and the pulse signals passing along the second signal pathway are further varied with respect to each other.

4. A device according to claim 1, wherein the pulse signal comprises an optical pulse signal.

5. A device according to claim 4, wherein the pulse signal comprises a laser pulse signal.

6. A device according to claim 1, wherein the pulse signal comprises an electrical signal.

7. A device according to claim 1, comprising a measuring apparatus configured to receive the signal pulse train.

8. A device according to claim 7, wherein the measuring apparatus is an oscilloscope.

9. A method of passively optimising a single uncharacterised pulse signal into a chain of pulse signal replicas, of which, at least one of the pulse signal replicas will be within a predetermined amplitude threshold range comprising the steps of: a) receiving a pulse signal to be measured; b) dividing the uncharacterised pulse signal into at least two separate pulse signals; each having different amplitude characteristics; c) applying a temporal delay to one of the separate pulse signals; d) combining the separate pulse signals into a consolidated signal train of pulses of increasing intensity.

10. A method according to claim 9, comprising the further step of sending the consolidated signal train to a measuring apparatus.

11. A method according to claim 9, wherein the received pulse signal comprises an optical pulse.

12. A method according to claim 9, wherein the received pulse signal comprises a laser pulse.

13. A method according to claim 9, wherein the received pulse signal comprises an electrical pulse.

14. A method according to claim 13 further comprising the step of converting the electrical pulse into an optical pulse.

Description

[0045] FIG. 1 Shows a schematic of a pulse replicator designed to produce four replicas of a laser pulse

[0046] The device itself may consist of series of nodes e.g. optical couplers, fibre optic couplers (or bulk beam splitters) and delay lines as shown in the FIGURE below.

[0047] FIG. 1 shows a schematic of a pulse replicator designed to produce four replicas of a laser pulse. The incident pulse (1) with unknown characteristics (2) in terms of amplitude and temporal profile, enters a first node (3) and is split into two pulses of differing amplitude and sent along at least two separate signal pathways formed from fibre optic pathways. The most intense pulse (5) is delayed by a time ‘t’ (4) before being passed to the second node (7). The other, weaker, pulse (6) passes directly to the second node (7). At the second node (7) some of the light from each of the signals is sent to each further output. The amount of light that propagates to each output is determined by the coupling ratio of the node (7). One of these outputs with characteristics (5&6) is passed directly to a third node (11) and the other output (8) is delayed, this time by a time ‘2*t’ and has the characteristics (9). These two outputs are combined in a third coupler (11) where the coupling ratio is selected such that the signal leaving from the first node output (12) consists of a chain of four pulses each of increasing intensity (13). This chain of pulses is then sent to a measuring device (not shown). Any residual light from the device leaves via the other arm of the node (14).

[0048] It is to be noted that the features disclosed in FIG. 1 provide an exemplary design including an intermediate node between the input node (3) and the output (11), in its most broad form the invention does not require intermediate nodes or the associated pathways between the intermediate node (7) and the output node (11). For clarity, the terms: input node (3) is also referred to as the first node, the intermediate node (7) as the second node and the output node (11) as the third node or coupler.

[0049] By judicious selection of the coupling ratios through the replication stages, at the output (12) a series of time separated replicas (13) of the incident pulse (1) is created with increasing intensity. In order to generate a series of four exponentially increasing pulses each ‘n’ times more intense than the previous one the splitting ratios should be set to values set below.

TABLE-US-00001 COMPONENT SPLITTING RATIO NODE 1 1:n NODE 2 1:1 NODE 3   1:n{circumflex over ( )}2

[0050] The series of separated replica (13) pulses termed a signal pulse train is then converted to an electrical signal using a photodiode (not shown) and recorded on an oscilloscope (not shown). Thus, the effective dynamic range of the measuring device is extended by ratio of the intensity of the first to last pulse replica. Through this method of generating time separated replicas with an increasing intensity characteristic it is assured that at least one of pulses will be within the dynamic range of the measuring instrument such as an oscilloscope improving the reliability of recording the original pulse with unknown temporal characteristics. It also ensures that the measurement device has not been blinded or saturated by an early high intensity pulse.

[0051] It will be understood by those skilled in the art that the optical couplers may have a dual function of both coupling received signals and then further dividing the signal further. They are also often alternatively referred to in the art as optical taps or splitters.

[0052] Furthermore, whilst this specific embodiment describes the replication of an optical signal it is to be appreciated that this method is similarly applicable to electrical signals and may comprise power dividers or directional couplers.

[0053] Depending upon the type and characteristics of the pulse signal to be processed, the fibre optic paths may be replaced by any suitable transmission path such as an electrical pathway.