CN112511220B

CN112511220B - Measuring method for rapidly and effectively judging multimode fiber bandwidth

Info

Publication number: CN112511220B
Application number: CN201910870844.4A
Authority: CN
Inventors: 孙安; 楚广虎; 袁燕飞; 汤钧; 崔明雷; 祝幸; 哈什昂·尼勒斯库马尔·潘迪亚; 庄焰
Original assignee: CHINA ELECTRONICS TECHNOLOGY GROUP Corp NO 23 RESEARCH INSTITUTE; Yongke Singapore Ltd; Huawei Technologies Co Ltd
Current assignee: CHINA ELECTRONICS TECHNOLOGY GROUP Corp NO 23 RESEARCH INSTITUTE; Yongke Singapore Ltd; Huawei Technologies Co Ltd
Priority date: 2019-09-16
Filing date: 2019-09-16
Publication date: 2022-02-22
Anticipated expiration: 2039-09-16
Also published as: CN112511220A

Abstract

Various embodiments relate to methods of determining bandwidth parameters of a device under test. The method may include providing an optical test signal to the device under test. The method may also include detecting a light-received signal from the device under test, the light-received signal based on the light test signal provided to the device under test. The method may also include generating a plurality of sampled waveforms based on the light-received signal. The method may also include determining a bandwidth parameter of the device under test. Determining the bandwidth parameter of the device under test may include determining a synthetic eye attenuation (SEA) based on the plurality of sampled waveforms and a plurality of sampled reference waveforms associated with the reference device.

Description

Measuring method for rapidly and effectively judging multimode fiber bandwidth

Technical Field

Various aspects of the present invention relate to a method of determining bandwidth parameters of a device under test. Various aspects of the invention may be directed to a test system for determining bandwidth parameters of a device under test.

Background

There are many methods designed to evaluate the performance of the entire optical communication system or various components in the optical communication system. For example, the institute for Electrical and electronics Engineers standards (IEEE Std)802.3bm-2015 gives and defines Transmitter and Dispersive Eye Closure (TDEC). TDEC is an efficient method of testing light emitters.

Different types of multimode optical fibers (OM1-5) have different effective bandwidth requirements, as described in IEC 60793-2-10. A typical test method for testing involves the use of a Differential Mode Dispersion (DMD) tester. However, the DMD tester can only test the fiber optic line without a connector. Furthermore, the fiber optic line must be sufficiently long due to DMD tester resolution (bandwidth) limitations. For fibre channel, most standards only provide Insertion Loss (IL) requirements. The insertion loss test is a quick and convenient method and is widely used for testing optical fiber channels.

For multimode fiber optic cables, there are two main factors that affect the performance of the cable after factory assembly. One factor is the quality of the connector and another factor is the bandwidth of the fiber optic line. Measuring Insertion Loss (IL) or Return Loss (RL) can detect most cables with poor connectors. However, for fiber optic lines, measuring insertion loss or return loss alone may not be sufficient to ensure that the cable meets the requirements for fast communication.

Most testers use a low speed signal or a Direct Current (DC) signal to measure Insertion Loss (IL) or attenuation. The main difference between different classes of fiber optic lines (e.g., OM3 and OM4) is the effective bandwidth (DMD effect), which affects the rising/falling edges of high speed signals. However, for low speed signals or DC signals, the effect may be negligible or not at all.

FIG. 1A (left) shows a 1 gigabit per second (Gbps) input pulse signal transmitted to 300m OM3 and 300m OM4 multimode fiber; and (right) output signals from OM3 fiber and OM4 fiber. FIG. 1B (left) shows a 25 gigabit/second (Gbps) input pulse signal transmitted to 300m OM3 and 300m OM4 multimode fiber; and (right) output signals from OM3 fiber and OM4 fiber. Fig. 1A-B show graphs of amplitude (in arbitrary units) as a function of time (in femtoseconds).

As shown in fig. 1A-B, there is no significant difference in output signals when the injection signal is a 1Gps pulse, and there is a significant difference in output signals when the injection signal is a 25Gbps pulse. Different grades of fiber (e.g., OM3 and OM4) may exhibit similar attenuation to low frequency signals. However, conventional testers may not be able to distinguish between different grades of optical fiber.

Disclosure of Invention

To this end, the object of the present invention is to provide a fast and cost-effective test system and method for determining parameters of a device under test.

Various embodiments of the invention may be directed to a method of determining bandwidth parameters of a device under test. The method may include providing an optical test signal to the device under test. The method may also include detecting a light receive signal from the device under test, the light receive signal being based on the optical test signal provided to the device under test. The method may further include generating a plurality of sampling waveforms based on the light reception signal. The method may also include determining a bandwidth parameter of the device under test. Determining the bandwidth parameter of the device under test may include determining a synthetic eye pattern attenuation (SEA) based on the plurality of sampled waveforms and a plurality of sampled reference waveforms associated with the reference device.

Various embodiments may be directed to a test system for determining bandwidth parameters of a device under test. The test system may comprise a transmitter unit configured to provide an optical test signal into the device under test. The test system may further comprise a receiver unit configured to detect the light reception signal from the device under test. The light receiving signal may be based on a light test signal provided to the device under test. The test system may further include a sampling unit configured to generate a plurality of sampling waveforms based on the light reception signal. The test system may additionally include a control unit configured to determine a bandwidth parameter of the device under test by determining a synthetic eye-pattern attenuation (SEA) based on the plurality of sampled waveforms and a plurality of sampled reference waveforms associated with the reference device.

Drawings

The invention will be better understood with reference to the detailed description when considered in conjunction with the non-limiting examples and the accompanying drawings, in which:

FIG. 1A (left) shows a 1 gigabit per second (Gbps) input pulse signal transmitted to 300m OM3 and 300m OM4 multimode fiber; and (right) output signals from OM3 fiber and OM4 fiber.

FIG. 1B (left) shows a 25 gigabit/second (Gbps) input pulse signal transmitted to 300m OM3 and 300m OM4 multimode fiber; and (right) output signals from OM3 fiber and OM4 fiber.

FIG. 2 is a general diagram illustrating a method of determining bandwidth parameters of a device under test in accordance with various embodiments.

FIG. 3 illustrates an optical test signal according to various embodiments.

FIG. 4 illustrates a sampled waveform generated in accordance with various embodiments.

FIG. 5 is a general diagram of a test system for determining bandwidth parameters of a device under test in accordance with various embodiments.

Detailed Description

The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized and structural and logical changes may be made without departing from the scope of the present invention. The various embodiments are not necessarily mutually exclusive, as some embodiments may be combined with one or more other embodiments to form new embodiments.

Embodiments described in the context of one of a method or test system are similarly valid for the other method or test system. Similarly, embodiments described in the context of methods are similarly valid for test systems, and vice versa.

Features described in the context of an embodiment may apply correspondingly to the same or similar features in other embodiments. Features described in the context of embodiments may be applied to other embodiments accordingly, even if not explicitly described in these other embodiments. Furthermore, additions and/or combinations and/or substitutions as described for features in the context of an embodiment may be correspondingly applied to the same or similar features in other embodiments.

The articles "a," "an," and "the" are used in relation to features or elements in the context of various embodiments to include reference to one or more features or elements.

In the context of various embodiments, the term "about" or "approximately" as applied to a numerical value includes both a precise value and a reasonable variance.

As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Various embodiments may seek to solve or mitigate the problems faced by conventional testers. Various embodiments may provide a fast and cost-effective way to estimate the bandwidth of an optical device, such as a multimode optical fiber.

FIG. 2 is a general diagram illustrating a method of determining bandwidth parameters of a device under test in accordance with various embodiments. The method may include providing an optical test signal to a device under test at 202. The method may further include detecting a light receive signal from the device under test at 204, the light receive signal being based on the optical test signal provided to the device under test. The method may also include generating a plurality of sampling waveforms based on the light reception signal at 206. The method may also include determining bandwidth parameters of the device under test at 208. Determining the bandwidth parameter of the device under test may include determining a synthetic eye-pattern attenuation (SEA) based on the plurality of sampled waveforms and a plurality of sampled reference waveforms associated with the reference device.

In other words, the method may include delivering an optical test signal (e.g., a continuous square wave signal) to a first end of a device under test (e.g., a cable, such as a multimode fiber optic cable). The method may also include detecting an output signal from a second terminal of the device under test. The output signal may be referred to as a "light reception signal". The optical test signal may be modified or distorted as it passes through the device under test to generate an optical receive signal. The modification or distortion may be affected by the optical characteristics of the device under test.

The output signal or the light-receiving signal may then be used to obtain a plurality of sampled waveforms. The plurality of sampled waveforms may each be an eye diagram. The output signal or the optical receive signal may be converted to an electrical receive signal, and the electrical receive signal may be sampled to generate the plurality of sampled waveforms. The plurality of sampling waveforms may be generated by sampling a number of points (N) per cycle of an electrical reception signal that is converted for a plurality (N) of cycles based on an optical reception signal.

The bandwidth parameters of the device under test may be determined or obtained by determining a composite eye pattern attenuation based on the plurality of sampled waveforms and a plurality of sampled reference waveforms generated from a reference device (rather than from the device under test).

The bandwidth parameter of the device under test may refer to the bandwidth of the device under test, or any other parameter of the device under test, which is derived or dependent on the bandwidth.

In various embodiments, the bandwidth parameters of the device under test may be determined based on the combined eye attenuation and threshold. The device under test may be a cable under test. Similarly, the reference device may be a reference cable.

As highlighted above, a bandwidth parameter of the device under test may be determined or obtained based on the integrated eye attenuation (SEA), which may be derived or determined from the plurality of sampled waveforms and the plurality of sampled reference waveforms.

In various embodiments, the plurality of sampled reference waveforms may be generated based on a reference light receive signal from a reference device. The reference light receive signal may be converted to a reference electrical receive signal, and the reference electrical receive signal may be sampled to generate the plurality of sampled reference waveforms. The plurality of sampling reference waveforms may be generated by sampling the number of dots (N) per cycle of a reference electrical received signal that is converted for a plurality (N) of cycles based on a reference optical received signal. The plurality of sampled reference waveforms may each be an eye diagram.

In other words, the plurality of sampled reference waveforms associated with the reference device may be generated in a similar manner as the plurality of sampled waveforms associated with the device under test. The optical test signal/optical reference test signal may be transmitted to the device under test/reference device, respectively, and the optical reception signal/reference optical reception signal may be output from the device under test/reference device, respectively. The light reception signal/reference light reception signal for the device under test/reference device may be converted into an electric reception signal/reference electric reception signal, respectively, and the electric reception signal/reference electric reception signal may be sampled to generate the plurality of sampling waveforms/the plurality of sampling reference waveforms.

The reference device may be a short length cable with the best performance in the evaluation scale and may be carefully selected to properly assemble with the best performance connector.

In various embodiments, determining the integrated eye attenuation (SEA) may comprise: for each sampled waveform, a separate area (A) surrounded by a separate perimeter is determined_i，t) To obtain a plurality of separate areas

(for n cycles); and determining an average area (A) based on the plurality of individual areas_t). Average area (A)_t) Can be represented by the equation

With the number of periods (n) and the respective area (A)_i) And (4) correlating.

In various embodiments, determining the integrated eye attenuation may further comprise: for each sampled reference waveform, an individual reference area (A) surrounded by an individual reference perimeter is determined_i，ref) To obtain a plurality of individual reference areas

(for n cycles); and determining an average reference area (A) based on the plurality of individual reference areas_ref). Average base area (A)_ref) Can be represented by the equation

With the number of periods (n) and the respective area (A)_i，ref) And (4) correlating.

Determining the integrated eye attenuation (SEA) may further comprise basing the average area (A) on_t) And average reference area (A)_ref) A composite eye attenuation is determined. Integrated eye attenuation (SEA), average area (a)_t) And average reference area (A)_ref) Can be represented by the equation

To be associated.

In various embodiments, the optical test signal may have a 50% duty cycle. In various embodiments, the optical test signal may be a square wave signal or a near square wave signal. A square wave can be defined as a periodic waveform in which the amplitude alternates at a steady frequency between a fixed minimum and maximum value, with the same minimum and maximum duration.

In various embodiments, the optical reference test signal may have a 50% duty cycle. The optical reference test signal may be a square wave signal or a near square wave signal.

FIG. 3 illustrates an optical test signal according to various embodiments. The optical test signal may be a continuous near square wave signal having a 50% duty cycle and may be injected into the device under test. The frequency of the optical test signal may be decided or determined according to the required bandwidth of the device under test. A frequency generator may be used to generate the required electrical transmit signal, and an optical transmitter (Tx) may convert the electrical transmit signal into an optical test signal for injection into the device under test through an optical switch (in a multi-channel setup) and a connector.

On the receiver side, an optical receiver (Rx) may convert an incoming optical signal (i.e., a received optical signal) into an electrical receive signal. A high bandwidth analog-to-digital converter (ADC) may sample the electrical received signal to generate the plurality of samplesAnd (4) sampling the waveform. The plurality of sampled waveforms may be transmitted to a control or display terminal. The ADC or sampling unit/sub-sampling system may be configured to sample N points in one period of the electrical receive signal corresponding to N points in one period of the optical test signal. The interval between two adjacent sampling points can be set by

Provided, where T is the cycle time of the optical test signal. A total of n cycles of the electrical receive signal, corresponding to the n cycles of the optical test signal, may be sampled and acquired to form the plurality of sampled waveforms.

The control unit may collect and process n cycles of the signal. FIG. 4 illustrates a sampled waveform generated in accordance with various embodiments. 1024 points (i.e., N-1024) may be sampled to form the waveform shown in fig. 4. Each sampled waveform may be generated from one cycle of the electrical received signal. Each sampled waveform may be an eye diagram.

The method may involve determining an area (a) encompassed by a periphery of each sampled waveform_i) As shown in fig. 4. Area A_iTwo regions surrounded by two "eyes" of the eye diagram may be included. Then can pass through

To provide an average enclosed area a over the n waveforms.

The test procedure may start with a calibration using a reference device. The reference device may be a short length cable with the best optical fiber of an evaluation grade (e.g., OM4 grade) and may be carefully selected to ensure that it is properly assembled with the best performing connector. If the device under test is a multi-channel cable, the reference device may have the same connection structure as the device under test.

The reference device may be tested using the previously emphasized process. The optical reference test signal may be communicated to a reference device, and the reference optical receive signal may be output from the reference device. The reference light receiving signal for the reference device can be converted into a reference electricity receiving signal, and the reference electricity can be converted into reference electricityThe received signal is sampled to generate the plurality of sampled reference waveforms. The bounding area A may be determined based on the plurality of sampled reference waveforms_ref。

The device under test may then be subsequently tested. The optical test signal may be passed into the device under test and the optical receive signal may be output from the device under test. The optical receive signal for the device under test may be converted to an electrical receive signal, and the electrical receive signal may be sampled to generate the plurality of sampled waveforms. The bounding area A may be determined based on the plurality of sampled waveforms_t。

Can pass through

Providing integrated eye attenuation (SEA).

A threshold may be defined and the SEA may be compared to the threshold to evaluate the device under test. The threshold may be defined based on theoretical studies and/or actual test results for a large number of cables of different grades.

Only a variety of embodiments may be required to use a square wave or near square wave as the test pattern. In contrast, typical eye test systems may use complex test patterns. By using a square wave or near-square wave, various embodiments may not require the use of complex signal pattern generators used in typical eye testing systems. Various embodiments may include or require a simple frequency synthesizer. This not only reduces system cost, but also allows the system to test different speed requirements.

Various embodiments involve determining an average of the signals over n cycles to calculate the enclosed area. In contrast, in a typical eye diagram test system, features of the eye diagram, such as Optical Modulation Amplitude (OMA), eye height, eye width, eye rise time, eye fall time, jitter, etc., are typically measured. These measurements may not be appropriate because the device under test is a passive static fiber optic cable. For example, while a passive cable may generate jitter, the jitter may be primarily from the test system itself, while the noise may be primarily from the test system rather than the cable. Eye height, eye width, and open eye estimates may all be affected by jitter and noise from the test system, and these jitter and noise may cause the measurements to be inaccurate for characterizing the device under test. Various embodiments may eliminate or reduce the effects of jitter and system noise by using an average of n cycles. Accordingly, various embodiments may be better suited to characterize the passive static device under test.

Further, as highlighted above, SEA may be defined as a_tAnd A_refThe ratio of (a) to (b). Based on this definition, the influence of the system itself (e.g., due to its bandwidth limitation, jitter, transmit (Tx) power, rise time/fall time effects on the transmit (Tx) side and the receive (Rx) side) is tested and waveform distortion and the like can be removed. In contrast to other conventional eye diagram parameters (e.g., OMA, eye height, eye width, eye rise time, eye fall time, jitter, etc.), SEA may be a suitable parameter representing characteristics of the device under test.

Experiments prove that, compared with other traditional eye diagram parameters, SEA is more stable and efficient in testing the bandwidth performance of the tested device.

FIG. 5 is a general diagram of a test system 500 for determining bandwidth parameters of a device under test, in accordance with various embodiments. The test system 500 may comprise a transmitter unit 502 configured to provide an optical test signal into the device under test. The test system 500 may further include a receiver unit 504 configured to detect light reception signals from the device under test. The light receiving signal may be based on a light test signal provided to the device under test. The test system 500 may further include a sampling unit 506 configured to generate a plurality of sampling waveforms based on the light reception signal. The test system 500 may additionally include a control unit 508 configured to determine a bandwidth parameter of the device under test by determining a synthetic eye-pattern attenuation (SEA) based on the plurality of sampled waveforms and a plurality of sampled reference waveforms associated with the reference device.

In other words, the test system 500 may include a transmitter unit 502 and a receiver unit 504. The transmitter unit 502 may provide an optical test signal to the device under test. The optical test signal may be modified or distorted as it passes through the device under test to form an optical receive signal that is received by the receiver unit 504. The test system 500 may further include a sampling unit 506 that generates a plurality of sampling waveforms based on the light reception signal. The control unit 508 may be configured to determine a bandwidth parameter of the device based on the plurality of sampled waveforms. This may be accomplished by determining a composite eye-pattern attenuation based on the plurality of sampled waveforms and a plurality of sampled reference waveforms associated with a reference device.

Fig. 5 is intended to illustrate various components of a system 500 according to various embodiments only, and not to limit the size, orientation, shape, arrangement, etc. of the various components.

The control unit 508 may be referred to as a controller 508. The control unit may comprise processing circuitry or a processor. The sampling unit 506 may be referred to as a sub-sampling system or circuit. The sampling unit 506 may be, for example, an analog-to-digital converter (ADC).

In various embodiments, transmitter unit 502, receiver unit 504, sampling unit 506, and control unit 508 may be different parts of a stand-alone device. In various other embodiments, a first device includes the transmitter unit 502 and a second device, separate from the first device, includes the receiver unit 504.

In various embodiments, sampling unit 506 may be coupled or connected to receiver unit 504. The control unit 508 may also be coupled or connected to the receiver unit 504, the sampling unit 506 and/or the transmitter unit 502. The control unit 508 may be configured to provide control signals to the receiver unit 504, the sampling unit 506 and/or the transmitter unit 502.

The bandwidth parameters of the device under test may be determined based on the combined eye pattern attenuation and the threshold. The plurality of sampled reference waveforms may be generated based on a reference light receive signal from a reference device.

In various embodiments, the transmitter unit 502 may comprise a frequency generator to generate the electrical transmission signal. The frequency generator may be a simple frequency synthesizer. The transmitter unit 502 may also include an optical transmitter (Tx) coupled or connected to a frequency generator. The optical transmitter may be configured to generate an optical test signal based on the electrical emission signal. The transmitter unit 502 may further comprise an optical switch for coupling with the device under test, i.e. the first side of the device under test. The optical switch may be coupled or connected to the optical transmitter. The optical test signal may be transmitted from the optical transmitter to the device under test through the optical switch. The optical test signal may be modified or distorted as it passes through the device under test (e.g., a multimode fiber optic cable) to form an optical receive signal.

In various embodiments, receiver unit 504 may include additional optical switches for coupling with the device under test. The receiver unit 504 may also include an optical receiver configured to receive an optical receive signal from the device under test. The optical receiver may be connected or coupled to a further optical switch and the optical receive signal may be passed from the device under test to the optical receiver via the further optical switch. The optical receiver may be configured to generate an electrical receive signal based on the optical receive signal. The sampling unit 506 may be coupled or connected to an optical receiver. The sampling unit 506 may be configured to generate a plurality of sampling waveforms by sampling the number of points (N) per cycle of the electrical reception signal, which is converted for a plurality of (N) cycles based on the optical reception signal.

The control unit 508 may be configured to receive the plurality of sampled waveforms from the sampling unit 506. The control unit 508 may be configured to obtain a plurality of separate areas by determining, for each sampled waveform, a separate area surrounded by a separate periphery; and determining a bandwidth parameter of the device under test by determining an average area based on the plurality of individual areas.

The control unit 508 may be further configured to obtain a plurality of individual reference areas by determining, for each sampled reference waveform, an individual reference area surrounded by an individual reference perimeter; determining an average reference area by based on a plurality of individual reference areas; and determining a bandwidth parameter of the device under test by determining a composite eye attenuation based on the average area and the average reference area.

In various embodiments, the plurality of sampled waveforms may each be an eye diagram. The plurality of sampled reference waveforms may each be an eye diagram.

In various embodiments, the optical test signal may have a 50% duty cycle. In various embodiments, the optical test signal may be a square wave signal or a near square wave signal.

In various embodiments, the device under test may be a multimode fiber optic cable.

While the present invention has been particularly shown and described with reference to particular embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The scope of the invention is, therefore, indicated by the appended claims, and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

1. a method for determining a bandwidth parameter of a device under test, is characterized in that, comprising:

providing an optical test signal to the device under test;

detecting a light-received signal from the device under test, the light-received signal based on an optical test signal provided to the device under test;

generating a plurality of sampled waveforms based on the light-received signal;

and determining the bandwidth parameter of the device under test;

Wherein, determining the bandwidth parameter of the device under test includes determining a comprehensive eye attenuation based on the plurality of sampled waveforms and the plurality of sampled reference waveforms associated with the reference device;

Wherein, the device under test is a multimode optical fiber cable, and the reference device is a reference cable;

Wherein, determining the comprehensive eye diagram attenuation includes: for each of the sampled waveforms, determining an individual area surrounded by an individual periphery to obtain a plurality of individual areas; and determining an average area based on the plurality of individual areas;

Wherein, determining the comprehensive eye diagram attenuation further includes: for each of the sampled reference waveforms, determining an individual reference area surrounded by an outer periphery of an individual reference to obtain a plurality of individual reference areas; determining an average based on the plurality of individual reference areas base area;

The composite eye attenuation is determined based on the average area and the average reference area.

2. method according to claim 1, is characterized in that:

A bandwidth parameter of the device under test is determined based on the composite eye attenuation and threshold.

3. method according to claim 1, is characterized in that:

The plurality of sampled reference waveforms are generated based on a reference light reception signal from the reference device.

4. method according to claim 1, is characterized in that:

The plurality of sampled waveforms are generated by sampling some (N) points per cycle of an electrical receive signal that is converted based on the light receive signal during a plurality of cycles.

5. method according to claim 1, is characterized in that:

Each of the plurality of sampled waveforms is an eye diagram.

6. The method according to claim 1, wherein:

The optical test signal has a 50% duty cycle.

7. The method according to claim 1, wherein:

The optical test signal is a square wave signal.

8. A test system for determining a bandwidth parameter of a device under test, comprising:

a transmitter unit configured to provide an optical test signal to the device under test;

a receiver unit configured to detect an optical reception signal from the device under test, the optical reception signal being based on an optical test signal provided to the device under test;

a sampling unit configured to generate a plurality of sampling waveforms based on the light-receiving signal;

and a control unit further configured to determine a bandwidth parameter of the device under test by determining a composite eye attenuation based on the plurality of sampled waveforms and a plurality of sampled reference waveforms associated with a reference device;

Wherein, the control unit is configured to determine the bandwidth parameter of the device under test by: determining, for each sampled waveform, a separate area surrounded by a separate periphery to obtain a plurality of separate areas; determining based on the plurality of separate areas average area;

Wherein, the control unit is further configured to determine the bandwidth parameter of the device under test by: for each sampled reference waveform, determining an individual reference area surrounded by an individual reference periphery to obtain a plurality of individual reference areas; The plurality of individual reference areas determine an average reference area; and the composite eye attenuation is determined based on the average area and the average reference area.

9. test system according to claim 8, is characterized in that:

10. The test system according to claim 8, wherein:

11. The test system according to claim 8, wherein:

The receiver unit includes an optical receiver configured to generate an electrical reception signal based on the optical reception signal;

and wherein, during a plurality of cycles, the sampling unit is configured to generate the plurality of sampled waveforms by sampling some (N) points per cycle of an electrical receive signal, the electrical receive signal being based on the light The received signal is converted.

12. The test system according to claim 8, wherein:

Each of the plurality of sampled waveforms is an eye diagram.

13. The test system according to claim 8, wherein:

The optical test signal has a 50% duty cycle.

14. The test system of claim 8, wherein:

The optical test signal is a square wave signal.