Editing Wavelength-division multiplexing (section)

==Dense WDM==
''Dense wavelength-division multiplexing'' (DWDM) refers originally to optical signals multiplexed within the 1550&nbsp;nm band so as to leverage the capabilities (and cost) of [[erbium-doped fiber amplifier]]s (EDFAs), which are effective for wavelengths between approximately 1525–1565&nbsp;nm ([[C band (infrared)|C band]]), or 1570–1610&nbsp;nm ([[L band (infrared)|L band]]). EDFAs were originally developed to replace [[SONET/SDH]] optical-electrical-optical (OEO) [[Regenerator (telecommunication)|regenerators]], which they have made practically obsolete. EDFAs can amplify any optical signal in their operating range, regardless of the modulated bit rate. In terms of multi-wavelength signals, so long as the EDFA has enough pump energy available to it, it can amplify as many optical signals as can be multiplexed into its amplification band (though signal densities are limited by choice of modulation format). EDFAs therefore allow a single-channel optical link to be upgraded in bit rate by replacing only equipment at the ends of the link, while retaining the existing EDFA or series of EDFAs through a long haul route. Furthermore, single-wavelength links using EDFAs can similarly be upgraded to WDM links at reasonable cost. The EDFA's cost is thus leveraged across as many channels as can be multiplexed into the 1550&nbsp;nm band. DWDM is used by carriers and between data centers for carrying large amounts of data.<ref>https://www.cisco.com/c/dam/global/de_at/assets/docs/dwdm.pdf</ref><ref>https://datacentrereview.com/2021/09/connecting-modern-data-centres-with-dwdm-technology/</ref>

===DWDM systems===
At this stage, a basic DWDM system contains several main components:

[[File:WDM modules 3.jpg|thumb|WDM multiplexer for DWDM communications]]
# A DWDM '''terminal multiplexer'''. The terminal multiplexer contains a wavelength-converting transponder for each data signal, an optical multiplexer and where necessary an optical amplifier (EDFA). Each wavelength-converting transponder receives an optical data signal from the client layer, such as SONET/SDH or another type of data signal, converts this signal into the electrical domain, and re-transmits the signal at a specific wavelength using a 1,550&nbsp;nm band laser. These data signals are then combined into a multi-wavelength optical signal using an optical multiplexer, for transmission over a single fiber (e.g., SMF-28 fiber). The terminal multiplexer may or may not also include a local transmit EDFA for power amplification of the multi-wavelength optical signal. In the mid-1990s DWDM systems contained 4 or 8 wavelength-converting transponders; by 2000 or so, commercial systems capable of carrying 128 signals were available. 
# An '''intermediate line repeater''' is placed approximately every 80–100&nbsp;km to compensate for the loss of optical power as the signal travels along the fiber. The 'multi-wavelength optical signal' is amplified by an EDFA, which usually consists of several amplifier stages.
# An '''intermediate optical terminal''', or '''optical add-drop multiplexer (OADM)'''. This is a remote amplification site that amplifies the multi-wavelength signal that may have traversed up to 140&nbsp;km or more before reaching the remote site. Optical diagnostics and telemetry are often extracted or inserted at such a site, to allow for localization of any fiber breaks or signal impairments. In more sophisticated systems (which are no longer point-to-point), several signals out of the multi-wavelength optical signal may be removed and dropped locally.
# A DWDM '''terminal demultiplexer'''. At the remote site, the terminal de-multiplexer consisting of an optical de-multiplexer and one or more wavelength-converting transponders separates the multi-wavelength optical signal back into individual data signals and outputs them on separate fibers for client-layer systems (such as SONET/SDH). Originally, this de-multiplexing was performed entirely passively, except for some telemetry, as most SONET systems can receive 1,550&nbsp;nm signals. However, in order to allow for transmission to remote client-layer systems (and to allow for digital domain signal integrity determination) such de-multiplexed signals are usually sent to O/E/O output transponders prior to being relayed to their client-layer systems. Often, the functionality of output transponder has been integrated into that of input transponder, so that most commercial systems have transponders that support bi-directional interfaces on both their 1,550&nbsp;nm (i.e., internal) side, and external (i.e., client-facing) side. Transponders in some systems supporting 40&nbsp;GHz nominal operation may also perform [[forward error correction]] (FEC) via [[Optical Transport Network|digital wrapper]] technology, as described in the [[ITU-T]] [[G.709]] standard.
# '''Optical Supervisory Channel (OSC)'''. This is data channel that uses an additional wavelength usually outside the EDFA amplification band (at 1,510&nbsp;nm, 1,620&nbsp;nm, 1,310&nbsp;nm or another proprietary wavelength). The OSC carries information about the multi-wavelength optical signal as well as remote conditions at the optical terminal or EDFA site. It is also normally used for remote software upgrades and user (i.e., network operator) Network Management information. It is the multi-wavelength analog to SONET's DCC (or supervisory channel). ITU standards suggest that the OSC should utilize an OC-3 signal structure, though some vendors have opted to use [[Fast Ethernet]] or another signal format. Unlike the 1550&nbsp;nm multi-wavelength signal containing client data, the OSC is always terminated at intermediate amplifier sites, where it receives local information before re-transmission.

The introduction of the ITU-T G.694.1<ref>{{cite web|title=ITU-T G.694.1, Spectral grids for WDM applications: DWDM frequency grid|url=http://www.itu.int/rec/T-REC-G.694.1/en|archive-url=https://web.archive.org/web/20121110070855/http://www.itu.int/rec/T-REC-G.694.1/en |archive-date=2012-11-10 }}</ref> [[frequency grid]] in 2002 has made it easier to integrate WDM with older but more standard SONET/SDH systems. WDM wavelengths are positioned in a grid having exactly 100&nbsp;GHz (about 0.8&nbsp;nm) spacing in optical frequency, with a reference frequency fixed at 193.10&nbsp;THz (1,552.52&nbsp;nm).<ref>DWDM ITU Table, 100&nbsp;Ghz spacing" [http://www.telecomengineering.com/downloads/DWDM%20ITU%20Table%20-%20100%20GHz.pdf telecomengineering.com] {{webarchive|url=https://web.archive.org/web/20080704124655/http://www.telecomengineering.com/downloads/DWDM%20ITU%20Table%20-%20100%20GHz.pdf |date=2008-07-04 }}</ref> The main grid is placed inside the optical fiber amplifier bandwidth, but can be extended to wider bandwidths. The first commercial deployment of DWDM was made by Ciena Corporation on the Sprint network in June 1996.<ref>{{cite news|last=Markoff|first=John|title=Fiber-Optic Technology Draws Record Stock Value|newspaper=The New York Times|date=March 3, 1997|url=https://www.nytimes.com/1997/03/03/business/fiber-optic-technology-draws-record-stock-value.html}}</ref><ref>{{cite journal|last=Hecht|first=Jeff|title=Boom, Bubble, Bust: The Fiber Optic Mania|journal=Optics and Photonics News|publisher=The Optical Society|page=47|date=October 2016|url=https://internethistory.org/wp-content/uploads/2020/01/OSA_Boom.Bubble.Bust_Fiber.Optic_.Mania_.pdf}}</ref><ref>{{cite web|title=New Technology Allows 1,600% Capacity Boost on Sprint's Fiber-Optic Network; Ciena Corp. System Installed; Greatly Increases Bandwidth|website=Sprint|date=June 12, 1996|url=https://www.thefreelibrary.com/NEW+TECHNOLOGY+ALLOWS+1,600+PERCENT+CAPACITY+BOOST+ON+SPRINT'S...-a018380396}}</ref> Today's DWDM systems use 50&nbsp;GHz or even 25&nbsp;GHz channel spacing for up to 160 channel operation.{{update-inline|date=January 2023}}<ref>{{cite web |url=http://www.infinera.com/products/ils2.html |title=Infinera Corporation &#124; Products &#124; Infinera Line System 1 |access-date=2012-03-19 |url-status=dead |archive-url=https://web.archive.org/web/20120327022231/http://www.infinera.com/products/ILS2.html |archive-date=2012-03-27 }}</ref>

DWDM systems have to maintain more stable wavelength or frequency than those needed for CWDM because of the closer spacing of the wavelengths. Precision temperature control of the laser transmitter is required in DWDM systems to prevent drift off a very narrow frequency window of the order of a few GHz. In addition, since DWDM provides greater maximum capacity it tends to be used at a higher level in the communications hierarchy than CWDM, for example on the [[Internet backbone]] and is therefore associated with higher modulation rates, thus creating a smaller market for DWDM devices with very high performance. These factors of smaller volume and higher performance result in DWDM systems typically being more expensive than CWDM.

Recent innovations in DWDM transport systems include pluggable and software-tunable transceiver modules capable of operating on 40 or 80 channels. This dramatically reduces the need for discrete spare pluggable modules, when a handful of pluggable devices can handle the full range of wavelengths.

===Wavelength-converting transponders===
{{tone|section|date=December 2018}}
Wavelength-converting transponders originally translated the transmit wavelength of a client-layer signal into one of the DWDM system's internal wavelengths in the 1,550&nbsp;nm band. External wavelengths in the 1,550&nbsp;nm most likely need to be translated, as they almost certainly do not have the required frequency stability tolerances nor the optical power necessary for the system's EDFA.

In the mid-1990s, however, wavelength-converting transponders rapidly took on the additional function of [[signal regeneration]]. Signal regeneration in transponders quickly evolved through 1R to 2R to 3R and into overhead-monitoring multi-bitrate 3R regenerators. These differences are outlined below:

; 1R: Retransmission. Basically, early transponders were [[garbage in, garbage out]] in that their output was nearly an analog ''copy'' of the received optical signal, with little signal cleanup occurring. This limited the reach of early DWDM systems because the signal had to be handed off to a client-layer receiver (likely from a different vendor) before the signal deteriorated too far. Signal monitoring was basically confined to optical domain parameters such as received power.

; 2R: Re-time and re-transmit. Transponders of this type were not very common and utilized a quasi-digital [[Schmitt trigger|Schmitt-triggering]] method for signal clean-up. Some rudimentary signal-quality monitoring was done by such transmitters that basically looked at analogue parameters.

; 3R: Re-time, re-transmit, re-shape. 3R Transponders were fully digital and normally able to view SONET/SDH section layer overhead bytes such as A1 and A2 to determine signal quality health. Many systems will offer {{nowrap|2.5 Gbit/s}} transponders, which will normally mean the transponder is able to perform 3R regeneration on OC-3/12/48 signals, and possibly gigabit Ethernet, and reporting on signal health by monitoring SONET/SDH section layer overhead bytes. Many transponders will be able to perform full multi-rate 3R in both directions. Some vendors offer {{nowrap|10 Gbit/s}} transponders, which will perform Section layer overhead monitoring to all rates up to and including OC-192.

; Muxponder: The [[muxponder]] (from multiplexed transponder) has different names depending on vendor. It essentially performs some relatively simple time-division multiplexing of lower-rate signals into a higher-rate carrier within the system (a common example is the ability to accept 4 OC-48s and then output a single OC-192 in the 1,550&nbsp;nm band). More recent muxponder designs have absorbed more and more TDM functionality, in some cases obviating the need for traditional [[SONET/SDH]] transport equipment.

===List of DWDM Channels===

For DWDM the range between C21-C60 is the most common range, for Mux/Demux in 8, 16, 40 or 96 sizes.<ref>{{cite web
|url=https://www.flexoptix.net/en/dwdm-channels/ 
|title=Flexoptix GmbH CWDM / DWDM CHANNELS
|access-date=2022-07-22
}}</ref><ref>{{cite web
|url=https://community.fs.com/news/cwdmdwdm-itu-channels-guide.html
|title=FS DWDM/CWDM Wavelength ITU Channels Guide
|date=12 July 2018
|access-date=2022-07-22
}}</ref>

{| class="wikitable sortable mw-collapsible mw-collapsed" style="text-align:right; vertical-align:middle;"
|+ 100&nbsp;GHz ITU Channels
|- style="text-align:center;"
! style="text-align:right;" | Channel #
! Center frequency (THz)
! Wavelength (nm)
|-
| 1
| style="text-align:center;" | 190.1
| style="text-align:left;" | 1577.03
|-
| 2
| style="text-align:center;" | 190.2
| style="text-align:left;" | 1576.2
|-
| 3
| style="text-align:center;" | 190.3
| style="text-align:left;" | 1575.37
|-
| 4
| style="text-align:center;" | 190.4
| style="text-align:left;" | 1574.54
|-
| 5
| style="text-align:center;" | 190.5
| style="text-align:left;" | 1573.71
|-
| 6
| style="text-align:center;" | 190.6
| style="text-align:left;" | 1572.89
|-
| 7
| style="text-align:center;" | 190.7
| style="text-align:left;" | 1572.06
|-
| 8
| style="text-align:center;" | 190.8
| style="text-align:left;" | 1571.24
|-
| 9
| style="text-align:center;" | 190.9
| style="text-align:left;" | 1570.42
|-
| 10
| style="text-align:center;" | 191.0
| style="text-align:left;" | 1569.59
|-
| 11
| style="text-align:center;" | 191.1
| style="text-align:left;" | 1568.77
|-
| 12
| style="text-align:center;" | 191.2
| style="text-align:left;" | 1567.95
|-
| 13
| style="text-align:center;" | 191.3
| style="text-align:left;" | 1567.13
|-
| 14
| style="text-align:center;" | 191.4
| style="text-align:left;" | 1566.31
|-
| 15
| style="text-align:center;" | 191.5
| style="text-align:left;" | 1565.5
|-
| 16
| style="text-align:center;" | 191.6
| style="text-align:left;" | 1564.68
|-
| 17
| style="text-align:center;" | 191.7
| style="text-align:left;" | 1563.86
|-
| 18
| style="text-align:center;" | 191.8
| style="text-align:left;" | 1563.05
|-
| 19
| style="text-align:center;" | 191.9
| style="text-align:left;" | 1562.23
|-
| 20
| style="text-align:center;" | 192.0
| style="text-align:left;" | 1561.41
|-
| 21
| style="text-align:center;" {{active|192.1}} 
| style="text-align:left;" | 1560.61
|-
| 22
| style="text-align:center;" {{active|192.2}} 
| style="text-align:left;" | 1559.79
|-
| 23
| style="text-align:center;" {{active|192.3}} 
| style="text-align:left;" | 1558.98
|-
| 24
| style="text-align:center;" {{active|192.4}} 
| style="text-align:left;" | 1558.17
|-
| 25
| style="text-align:center;" {{active|192.5}} 
| style="text-align:left;" | 1557.36
|-
| 26
| style="text-align:center;" {{active|192.6}} 
| style="text-align:left;" | 1556.55
|-
| 27
| style="text-align:center;" {{active|192.7}} 
| style="text-align:left;" | 1555.75
|-
| 28
| style="text-align:center;" {{active|192.8}} 
| style="text-align:left;" | 1554.94
|-
| 29
| style="text-align:center;" {{active|192.9}} 
| style="text-align:left;" | 1554.13
|-
| 30
| style="text-align:center;" {{active|193.0}} 
| style="text-align:left;" | 1553.33
|-
| 31
| style="text-align:center;" {{active|193.1}} 
| style="text-align:left;" | 1552.52
|-
| 32
| style="text-align:center;" {{active|193.2}} 
| style="text-align:left;" | 1551.72
|-
| 33
| style="text-align:center;" {{active|193.3}}
| style="text-align:left;" | 1550.92
|-
| 34
| style="text-align:center;" {{active|193.4}}
| style="text-align:left;" | 1550.12
|-
| 35
| style="text-align:center;" {{active|193.5}}
| style="text-align:left;" | 1549.32
|-
| 36
| style="text-align:center;" {{active|193.6}}
| style="text-align:left;" | 1548.51
|-
| 37
| style="text-align:center;" {{active|193.7}}
| style="text-align:left;" | 1547.72
|-
| 38
| style="text-align:center;" {{active|193.8}}
| style="text-align:left;" | 1546.92
|-
| 39
| style="text-align:center;" {{active|193.9}}
| style="text-align:left;" | 1546.12
|-
| 40
| style="text-align:center;" {{active|194.0}}
| style="text-align:left;" | 1545.32
|-
| 41
| style="text-align:center;" {{active|194.1}}
| style="text-align:left;" | 1544.53
|-
| 42
| style="text-align:center;" {{active|194.2}}
| style="text-align:left;" | 1543.73
|-
| 43
| style="text-align:center;" {{active|194.3}}
| style="text-align:left;" | 1542.94
|-
| 44
| style="text-align:center;" {{active|194.4}}
| style="text-align:left;" | 1542.14
|-
| 45
| style="text-align:center;" {{active|194.5}}
| style="text-align:left;" | 1541.35
|-
| 46
| style="text-align:center;" {{active|194.6}}
| style="text-align:left;" | 1540.56
|-
| 47
| style="text-align:center;" {{active|194.7}}
| style="text-align:left;" | 1539.77
|-
| 48
| style="text-align:center;" {{active|194.8}}
| style="text-align:left;" | 1538.98
|-
| 49
| style="text-align:center;" {{active|194.9}}
| style="text-align:left;" | 1538.19
|-
| 50
| style="text-align:center;" {{active|195.0}}
| style="text-align:left;" | 1537.4
|-
| 51
| style="text-align:center;" {{active|195.1}}
| style="text-align:left;" | 1536.61
|-
| 52
| style="text-align:center;" {{active|195.2}}
| style="text-align:left;" | 1535.82
|-
| 53
| style="text-align:center;" {{active|195.3}}
| style="text-align:left;" | 1535.04
|-
| 54
| style="text-align:center;" {{active|195.4}}
| style="text-align:left;" | 1534.25
|-
| 55
| style="text-align:center;" {{active|195.5}}
| style="text-align:left;" | 1533.47
|-
| 56
| style="text-align:center;" {{active|195.6}}
| style="text-align:left;" | 1532.68
|-
| 57
| style="text-align:center;" {{active|195.7}}
| style="text-align:left;" | 1531.9
|-
| 58
| style="text-align:center;" {{active|195.8}}
| style="text-align:left;" | 1531.12
|-
| 59
| style="text-align:center;" {{active|195.9}}
| style="text-align:left;" | 1530.33
|-
| 60
| style="text-align:center;" {{active|196.0}}
| style="text-align:left;" | 1529.55
|-
| 61
| style="text-align:center;" | 196.1
| style="text-align:left;" | 1528.77
|-
| 62
| style="text-align:center;" | 196.2
| style="text-align:left;" | 1527.99
|-
| 63
| style="text-align:center;" | 196.3
| style="text-align:left;" | 1527.22
|-
| 64
| style="text-align:center;" | 196.4
| style="text-align:left;" | 1526.44
|-
| 65
| style="text-align:center;" | 196.5
| style="text-align:left;" | 1525.66
|-
| 66
| style="text-align:center;" | 196.6
| style="text-align:left;" | 1524.89
|-
| 67
| style="text-align:center;" | 196.7
| style="text-align:left;" | 1524.11
|-
| 68
| style="text-align:center;" | 196.8
| style="text-align:left;" | 1523.34
|-
| 69
| style="text-align:center;" | 196.9
| style="text-align:left;" | 1522.56
|-
| 70
| style="text-align:center;" | 197.0
| style="text-align:left;" | 1521.79
|-
| 71
| style="text-align:center;" | 197.1
| style="text-align:left;" | 1521.02
|-
| 72
| style="text-align:center;" | 197.2
| style="text-align:left;" | 1520.25
|}

{| class="wikitable sortable mw-collapsible mw-collapsed" style="text-align:right; vertical-align:middle;"
|+ 50&nbsp;GHz ITU Channels
|- style="text-align:center;"
! Channel #
! Center frequency (THz)
! Wavelength (nm)
|-
| style="text-align:right;" | 1
| 190.1
| 1577.03
|-
| style="text-align:right;" | 1.5
| 190.15
| 1576.61
|-
| style="text-align:right;" | 2
| 190.2
| 1576.2
|-
| style="text-align:right;" | 2.5
| 190.25
| 1575.78
|-
| style="text-align:right;" | 3
| 190.3
| 1575.37
|-
| style="text-align:right;" | 3.5
| 190.35
| 1574.95
|-
| style="text-align:right;" | 4
| 190.4
| 1574.54
|-
| style="text-align:right;" | 4.5
| 190.45
| 1574.13
|-
| style="text-align:right;" | 5
| 190.5
| 1573.71
|-
| style="text-align:right;" | 5.5
| 190.55
| 1573.3
|-
| style="text-align:right;" | 6
| 190.6
| 1572.89
|-
| style="text-align:right;" | 6.5
| 190.65
| 1572.48
|-
| style="text-align:right;" | 7
| 190.7
| 1572.06
|-
| style="text-align:right;" | 7.5
| 190.75
| 1571.65
|-
| style="text-align:right;" | 8
| 190.8
| 1571.24
|-
| style="text-align:right;" | 8.5
| 190.85
| 1570.83
|-
| style="text-align:right;" | 9
| 190.9
| 1570.42
|-
| style="text-align:right;" | 9.5
| 190.95
| 1570.01
|-
| style="text-align:right;" | 10
| 191
| 1569.59
|-
| style="text-align:right;" | 10.5
| 191.05
| 1569.18
|-
| style="text-align:right;" | 11
| 191.1
| 1568.77
|-
| style="text-align:right;" | 11.5
| 191.15
| 1568.36
|-
| style="text-align:right;" | 12
| 191.2
| 1567.95
|-
| style="text-align:right;" | 12.5
| 191.25
| 1567.54
|-
| style="text-align:right;" | 13
| 191.3
| 1567.13
|-
| style="text-align:right;" | 13.5
| 191.35
| 1566.72
|-
| style="text-align:right;" | 14
| 191.4
| 1566.31
|-
| style="text-align:right;" | 14.5
| 191.45
| 1565.9
|-
| style="text-align:right;" | 15
| 191.5
| 1565.5
|-
| style="text-align:right;" | 15.5
| 191.55
| 1565.09
|-
| style="text-align:right;" | 16
| 191.6
| 1564.68
|-
| style="text-align:right;" | 16.5
| 191.65
| 1564.27
|-
| style="text-align:right;" | 17
| 191.7
| 1563.86
|-
| style="text-align:right;" | 17.5
| 191.75
| 1563.45
|-
| style="text-align:right;" | 18
| 191.8
| 1563.05
|-
| style="text-align:right;" | 18.5
| 191.85
| 1562.64
|-
| style="text-align:right;" | 19
| 191.9
| 1562.23
|-
| style="text-align:right;" | 19.5
| 191.95
| 1561.83
|-
| style="text-align:right;" | 20
| 192
| 1561.42
|-
| style="text-align:right;" | 20.5
| 192.05
| 1561.01
|-
| style="text-align:right;" | 21
| 192.1
| 1560.61
|-
| style="text-align:right;" | 21.5
| 192.15
| 1560.2
|-
| style="text-align:right;" | 22
| 192.2
| 1559.79
|-
| style="text-align:right;" | 22.5
| 192.25
| 1559.39
|-
| style="text-align:right;" | 23
| 192.3
| 1558.98
|-
| style="text-align:right;" | 23.5
| 192.35
| 1558.58
|-
| style="text-align:right;" | 24
| 192.4
| 1558.17
|-
| style="text-align:right;" | 24.5
| 192.45
| 1557.77
|-
| style="text-align:right;" | 25
| 192.5
| 1557.36
|-
| style="text-align:right;" | 25.5
| 192.55
| 1556.96
|-
| style="text-align:right;" | 26
| 192.6
| 1556.56
|-
| style="text-align:right;" | 26.5
| 192.65
| 1556.15
|-
| style="text-align:right;" | 27
| 192.7
| 1555.75
|-
| style="text-align:right;" | 27.5
| 192.75
| 1555.34
|-
| style="text-align:right;" | 28
| 192.8
| 1554.94
|-
| style="text-align:right;" | 28.5
| 192.85
| 1554.54
|-
| style="text-align:right;" | 29
| 192.9
| 1554.13
|-
| style="text-align:right;" | 29.5
| 192.95
| 1553.73
|-
| style="text-align:right;" | 30
| 193
| 1553.33
|-
| style="text-align:right;" | 30.5
| 193.05
| 1552.93
|-
| style="text-align:right;" | 31
| 193.1
| 1552.52
|-
| style="text-align:right;" | 31.5
| 193.15
| 1552.12
|-
| style="text-align:right;" | 32
| 193.2
| 1551.72
|-
| style="text-align:right;" | 32.5
| 193.25
| 1551.32
|-
| style="text-align:right;" | 33
| 193.3
| 1550.92
|-
| style="text-align:right;" | 33.5
| 193.35
| 1550.52
|-
| style="text-align:right;" | 34
| 193.4
| 1550.12
|-
| style="text-align:right;" | 34.5
| 193.45
| 1549.72
|-
| style="text-align:right;" | 35
| 193.5
| 1549.32
|-
| style="text-align:right;" | 35.5
| 193.55
| 1548.91
|-
| style="text-align:right;" | 36
| 193.6
| 1548.52
|-
| style="text-align:right;" | 36.5
| 193.65
| 1548.11
|-
| style="text-align:right;" | 37
| 193.7
| 1547.72
|-
| style="text-align:right;" | 37.5
| 193.75
| 1547.32
|-
| style="text-align:right;" | 38
| 193.8
| 1546.92
|-
| style="text-align:right;" | 38.5
| 193.85
| 1546,52
|-
| style="text-align:right;" | 39
| 193.9
| 1546,12
|-
| style="text-align:right;" | 39.5
| 193.95
| 1545.72
|-
| style="text-align:right;" | 40
| 194
| 1545.32
|-
| style="text-align:right;" | 40.5
| 194.05
| 1544.92
|-
| style="text-align:right;" | 41
| 194.1
| 1544.53
|-
| style="text-align:right;" | 41.5
| 194.15
| 1544.13
|-
| style="text-align:right;" | 42
| 194.2
| 1543.73
|-
| style="text-align:right;" | 42.5
| 194.25
| 1543.33
|-
| style="text-align:right;" | 43
| 194.3
| 1542.94
|-
| style="text-align:right;" | 43.5
| 194.35
| 1542.54
|-
| style="text-align:right;" | 44
| 194.4
| 1542.14
|-
| style="text-align:right;" | 44.5
| 194.45
| 1541.75
|-
| style="text-align:right;" | 45
| 194.5
| 1541.35
|-
| style="text-align:right;" | 45.5
| 194.55
| 1540.95
|-
| style="text-align:right;" | 46
| 194.6
| 1540.56
|-
| style="text-align:right;" | 46.5
| 194.65
| 1540.16
|-
| style="text-align:right;" | 47
| 194.7
| 1539.77
|-
| style="text-align:right;" | 47.5
| 194.75
| 1539.37
|-
| style="text-align:right;" | 48
| 194.8
| 1538.98
|-
| style="text-align:right;" | 48.5
| 194.85
| 1538.58
|-
| style="text-align:right;" | 49
| 194.9
| 1538.19
|-
| style="text-align:right;" | 49.5
| 194.95
| 1537.79
|-
| style="text-align:right;" | 50
| 195
| 1537.4
|-
| style="text-align:right;" | 50.5
| 195.05
| 1537
|-
| style="text-align:right;" | 51
| 195.1
| 1536.61
|-
| style="text-align:right;" | 51.5
| 195.15
| 1536.22
|-
| style="text-align:right;" | 52
| 195.2
| 1535.82
|-
| style="text-align:right;" | 52.5
| 195.25
| 1535.43
|-
| style="text-align:right;" | 53
| 195.3
| 1535.04
|-
| style="text-align:right;" | 53.5
| 195.35
| 1534.64
|-
| style="text-align:right;" | 54
| 195.4
| 1534.25
|-
| style="text-align:right;" | 54.5
| 195.45
| 1533.86
|-
| style="text-align:right;" | 55
| 195.5
| 1533.47
|-
| style="text-align:right;" | 55.5
| 195.55
| 1533.07
|-
| style="text-align:right;" | 56
| 195.6
| 1532.68
|-
| style="text-align:right;" | 56.5
| 195.65
| 1532.29
|-
| style="text-align:right;" | 57
| 195.7
| 1531.9
|-
| style="text-align:right;" | 57.5
| 195.75
| 1531.51
|-
| style="text-align:right;" | 58
| 195.8
| 1531.12
|-
| style="text-align:right;" | 58.5
| 195.85
| 1530.72
|-
| style="text-align:right;" | 59
| 195.9
| 1530.33
|-
| style="text-align:right;" | 59.5
| 195.95
| 1529.94
|-
| style="text-align:right;" | 60
| 196
| 1529.55
|-
| style="text-align:right;" | 60.5
| 196.05
| 1529.16
|-
| style="text-align:right;" | 61
| 196.1
| 1528.77
|-
| style="text-align:right;" | 61.5
| 196.15
| 1528.38
|-
| style="text-align:right;" | 62
| 196.2
| 1527.99
|-
| style="text-align:right;" | 62.5
| 196.25
| 1527.6
|-
| style="text-align:right;" | 63
| 196.3
| 1527.22
|-
| style="text-align:right;" | 63.5
| 196.35
| 1526.83
|-
| style="text-align:right;" | 64
| 196.4
| 1526.44
|-
| style="text-align:right;" | 64.5
| 196.45
| 1526.05
|-
| style="text-align:right;" | 65
| 196.5
| 1525.66
|-
| style="text-align:right;" | 65.5
| 196.55
| 1525.27
|-
| style="text-align:right;" | 66
| 196.6
| 1524.89
|-
| style="text-align:right;" | 66.5
| 196.65
| 1524.5
|-
| style="text-align:right;" | 67
| 196.7
| 1524.11
|-
| style="text-align:right;" | 67.5
| 196.75
| 1523.72
|-
| style="text-align:right;" | 68
| 196.8
| 1523.34
|-
| style="text-align:right;" | 68.5
| 196.85
| 1522.95
|-
| style="text-align:right;" | 69
| 196.9
| 1522.56
|-
| style="text-align:right;" | 69.5
| 196.95
| 1522.18
|-
| style="text-align:right;" | 70
| 197
| 1521.79
|-
| style="text-align:right;" | 70.5
| 197.05
| 1521.4
|-
| style="text-align:right;" | 71
| 197.1
| 1521.02
|-
| style="text-align:right;" | 71.5
| 197.15
| 1520.63
|-
| style="text-align:right;" | 72
| 197.2
| 1520.25
|-
| style="text-align:right;" | 72.5
| 197.25
| 1519.86
|}

===Reconfigurable optical add-drop multiplexer (ROADM)===
{{Main|Reconfigurable optical add-drop multiplexer}}
As mentioned above, intermediate optical amplification sites in DWDM systems may allow for the dropping and adding of certain wavelength channels. In most systems deployed as of August 2006 this is done infrequently, because adding or dropping wavelengths requires manually inserting or replacing wavelength-selective cards. This is costly, and in some systems requires that all active traffic be removed from the DWDM system because inserting or removing the wavelength-specific cards interrupts the multi-wavelength optical signal.

With a ROADM, network operators can remotely reconfigure the multiplexer by sending soft commands. The architecture of the ROADM is such that dropping or adding wavelengths does not interrupt the ''pass-through'' channels. Numerous technological approaches are utilized for various commercial ROADMs, the tradeoff being between cost, optical power, and flexibility.

===Optical cross connects (OXCs)===
{{Main|Optical cross-connect}}
{{Expand section|date=June 2008}}
When the network topology is a mesh, where nodes are interconnected by fibers to form an arbitrary graph, an additional fiber interconnection device is needed to route the signals from an input port to the desired output port. These devices are called optical crossconnectors (OXCs). Various categories of OXCs include electronic ("opaque"), optical ("transparent"), and wavelength-selective devices.