13.4 High-Speed Lightwave Transceivers
535
management, electromagnetic interference (EMI) management, and a management
data input/output (MDIO) interface for Ethernet data management.
13.4.4 Links Operating at 400 Gb/s and Higher
Building on the success of single-channel 10-, 40-, and 100-Gb/s links, the next
development step was the creation of ultrafast gigabit and terabit links running at
400 and 800 Gb/s and higher [20–22]. The implementation of 400-Gb/s systems
achieves a spectral efficiency up to 8 b/s/Hz and provides a fourfold increase in the
transport capacity of a 100-Gb/s system. Similar to the links operating up to 100 Gb/s,
the development of 400-Gb/s links is based on the standard 50-GHz DWDM grid,
thereby making them compatible with existing reconfigurable optical add/drop multiplexing (ROADM) optical networks (see Sect. 13.5). The modulation techniques for
achieving such high-speed networks include various high-order quadrature amplitude
modulation (QAM) formats and the concept of optical orthogonal frequency-division
multiplexing (OFDM).
13.5 Schemes for Optical Add/Drop Multiplexing
An optical add/drop multiplexer (OADM) is a device that allows the insertion or
extraction of one or more wavelengths from a fiber at a network node. For example,
an OADM might have the capability to drop and insert three wavelengths from a
set of N being transported over a single fiber. The remaining (N – 3) wavelengths
pass unaffected through (also called express through) the OADM to the next node.
Without an OADM, if only three wavelengths out of N 3 are needed at the local
node, then all the other wavelengths also would need to be processed there by means
of optoelectronic transceivers. This will greatly increase the equipment costs at that
node. Thus the advantage of the add/drop function is that no signal processing is
required for the set of wavelengths that passes straight through the OADM.
The OADM can reside at an optical amplifier site in a long-haul network or it
can be located at a node in a metro network. Depending on how it is designed, an
OADM can operate either statically in a fixed add/drop configuration or it can be
reconfigured dynamically from a remote network management site. A fixed optical
add/drop multiplexer is simply referred to as an OADM. A dynamic device is called
a reconfigurable OADM (ROADM) [23–25]. A fixed OADM obviously is not as
flexible as a ROADM and may require a change of hardware components if a different
set of wavelengths needs to be dropped or added.
Depending on whether an engineer is designing a metro or a long-haul network,
different performance specifications need to be addressed when implementing an
optical add/drop capability in the network. In general, because of the nature of the
services provided, changes in the add/drop configuration for a long-haul network
535
management, electromagnetic interference (EMI) management, and a management
data input/output (MDIO) interface for Ethernet data management.
13.4.4 Links Operating at 400 Gb/s and Higher
Building on the success of single-channel 10-, 40-, and 100-Gb/s links, the next
development step was the creation of ultrafast gigabit and terabit links running at
400 and 800 Gb/s and higher [20–22]. The implementation of 400-Gb/s systems
achieves a spectral efficiency up to 8 b/s/Hz and provides a fourfold increase in the
transport capacity of a 100-Gb/s system. Similar to the links operating up to 100 Gb/s,
the development of 400-Gb/s links is based on the standard 50-GHz DWDM grid,
thereby making them compatible with existing reconfigurable optical add/drop multiplexing (ROADM) optical networks (see Sect. 13.5). The modulation techniques for
achieving such high-speed networks include various high-order quadrature amplitude
modulation (QAM) formats and the concept of optical orthogonal frequency-division
multiplexing (OFDM).
13.5 Schemes for Optical Add/Drop Multiplexing
An optical add/drop multiplexer (OADM) is a device that allows the insertion or
extraction of one or more wavelengths from a fiber at a network node. For example,
an OADM might have the capability to drop and insert three wavelengths from a
set of N being transported over a single fiber. The remaining (N – 3) wavelengths
pass unaffected through (also called express through) the OADM to the next node.
Without an OADM, if only three wavelengths out of N 3 are needed at the local
node, then all the other wavelengths also would need to be processed there by means
of optoelectronic transceivers. This will greatly increase the equipment costs at that
node. Thus the advantage of the add/drop function is that no signal processing is
required for the set of wavelengths that passes straight through the OADM.
The OADM can reside at an optical amplifier site in a long-haul network or it
can be located at a node in a metro network. Depending on how it is designed, an
OADM can operate either statically in a fixed add/drop configuration or it can be
reconfigured dynamically from a remote network management site. A fixed optical
add/drop multiplexer is simply referred to as an OADM. A dynamic device is called
a reconfigurable OADM (ROADM) [23–25]. A fixed OADM obviously is not as
flexible as a ROADM and may require a change of hardware components if a different
set of wavelengths needs to be dropped or added.
Depending on whether an engineer is designing a metro or a long-haul network,
different performance specifications need to be addressed when implementing an
optical add/drop capability in the network. In general, because of the nature of the
services provided, changes in the add/drop configuration for a long-haul network