584
14 Basic Measurement and Monitoring Techniques
touchscreen or they can be sent via Bluetooth links or wireless connections to storage
devices or more sophisticated data analysis instruments.
14.2.4 Optical Attenuators
In many laboratory or production tests, the characteristics of a high optical signal
level may need to be measured. For example, if the level is a strong output from
an optical amplifier, the signal may need to be attenuated precisely before being
measured. This is done to prevent instrument damage or to avoid overload distortion
in the measurements. An optical attenuator allows a test engineer to reduce an optical
signal level up to, for example, 60 dB (a factor of 10
6 ) in precise steps at a specified
wavelength, which is usually 1310 or 1550 nm. At the lower performance end, these
attenuators are small devices (approximately 2 × 5 × 10 cm) intended for quick field
measurements that may only need to be accurate to 0.5 dB. Laboratory instruments
may have an attenuation precision of 0.001 dB.
14.2.5 OTN Tester for Performance Verification
A major concern in the implementation of an optical transport network (OTN) is how
to verify that the various network elements are functioning properly. In relation to
this, the ITU-T has published the following guidelines:
• G.709, Interfaces for the OTN (June 2020)
• G.798, Characteristics of OTN Hierarchy
Functional Blocks (Dec. 2017; Amend. 3, Jan. 2021)
Of particular importance is verification that the OTN elements that may have
been designed, produced, and installed by different vendors conform to these ITU-T
recommendations. Such tests, which are known as conformance tests, include the
following:
• Verifying the correctness of the interface specifications of the elements
• Checking the correct responses of the device under test (DUT)
• Verifying the correct behavior of forward-error-correcting (FEC) modules
• Examining that mapping of client signals are performed correctly
Multifunction, multiport, multiuser portable laptop-sized instruments for field
conformance testing can characterize parameters such as physical-layer jitter,
wander, and bit-error rate testing from 1.5 Mb/s to 100 Gb/s with the results displayed
in various formats on a 9-in. or larger screen.
14 Basic Measurement and Monitoring Techniques
touchscreen or they can be sent via Bluetooth links or wireless connections to storage
devices or more sophisticated data analysis instruments.
14.2.4 Optical Attenuators
In many laboratory or production tests, the characteristics of a high optical signal
level may need to be measured. For example, if the level is a strong output from
an optical amplifier, the signal may need to be attenuated precisely before being
measured. This is done to prevent instrument damage or to avoid overload distortion
in the measurements. An optical attenuator allows a test engineer to reduce an optical
signal level up to, for example, 60 dB (a factor of 10
6 ) in precise steps at a specified
wavelength, which is usually 1310 or 1550 nm. At the lower performance end, these
attenuators are small devices (approximately 2 × 5 × 10 cm) intended for quick field
measurements that may only need to be accurate to 0.5 dB. Laboratory instruments
may have an attenuation precision of 0.001 dB.
14.2.5 OTN Tester for Performance Verification
A major concern in the implementation of an optical transport network (OTN) is how
to verify that the various network elements are functioning properly. In relation to
this, the ITU-T has published the following guidelines:
• G.709, Interfaces for the OTN (June 2020)
• G.798, Characteristics of OTN Hierarchy
Functional Blocks (Dec. 2017; Amend. 3, Jan. 2021)
Of particular importance is verification that the OTN elements that may have
been designed, produced, and installed by different vendors conform to these ITU-T
recommendations. Such tests, which are known as conformance tests, include the
following:
• Verifying the correctness of the interface specifications of the elements
• Checking the correct responses of the device under test (DUT)
• Verifying the correct behavior of forward-error-correcting (FEC) modules
• Examining that mapping of client signals are performed correctly
Multifunction, multiport, multiuser portable laptop-sized instruments for field
conformance testing can characterize parameters such as physical-layer jitter,
wander, and bit-error rate testing from 1.5 Mb/s to 100 Gb/s with the results displayed
in various formats on a 9-in. or larger screen.