Dec
Technical Information
Data Centre Interconnect Systems for long haul high capacity data services
INTRODUCTION
With the introduction of SMPTE 2022-6 and ST2110 video over IP, as replacements for traditional SDI transport, it has become possible to design new production workflows with distributed switching topologies and remote production capability. In ST2110 systems multiple IP streams carrying all sources of video, audio and ancillary data can be sent between locations, as well as return feeds for program monitoring, talkback etc. With relatively high cost and limited availability of fibres over long distance being an issue, Data Centre Interconnect (DCI) systems using wavelength division multiplexing and in some cases coherent high speed optics can provide a solution.
Starting with SMPTE 2022-6 and in some cases compressed JPEG, feeds external to the studio could be reliably sent over comparatively low bandwidth connections. The signals encapsulated all the SDI, video, audio, ancillary data and timing information and typically a programme would be produced locally and sent to the studio for incorporating into the production before playout.
ST2110 takes things one step further, and by separating out the essence elements into individual video, audio and ancillary streams allows the remote production site to become more integrated with the studio production workflow. This can lead to a higher number of signals being sent between the two locations, potentially maintaining a UHD workflow, and in some cases over greater distances than have been envisaged previously.
DCI Box Solutions from Gigalight
GIGALIGHT provides a series of affordable DWDM and coherent optical transmission subsystems (DCI BOX) with all-in-one rack chassis design and ultra high capacity (up to 6.4Tb/s for 2U rack chassis) for data centre interconnection (DCI) and other long-haul transmission applications.
The DCI BOX transport platform contains the optical layer service cards (EDFA, VOA, and OLP etc.) and the electrical layer service cards (100G/200G/400G Optical Transport Unit OTU or muxponder). The DCI box forms the basis for an end-to-end DWDM platform and users can customise the setup with various add in cards, choosing between standard and coherent optics in the C band or O band, and amplification / compensation where required. Extensive monitoring gives users the ability to set parameter and monitor with alarms the complete optical path.
1U 1.6 T DCI Box from Gigalight
C-band DWDM operates in the Conventional band (≈1530–1565 nm), the most widely used wavelength window in long-haul and metro optical networks.
The C-band is popular because it offers:
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Low fibre attenuation
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Compatibility with powerful Erbium-Doped Fibre Amplifiers (EDFAs)
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A mature ecosystem of coherent transceivers, ROADMs, and optical components
C-band DWDM packs many tightly spaced wavelengths into this range, enabling very high-capacity, long-distance transmission for backbone and data-centre interconnect networks.
Below is a table of common ITU-T DWDM C-band frequencies (100 GHz grid), covering channels 192.0–196.1 THz, which correspond roughly to 1560–1530 nm.
C-band DWDM Frequency Table (100 GHz Grid)
| Channel – THz – nm | Channel – THz – nm | Channel – THz – nm | Channel – THz – nm |
|---|---|---|---|
| 20 – 192.0 – 1561.42 | 31 – 193.1 – 1552.52 | 42 – 194.2 – 1543.73 | 53 – 195.3 – 1534.96 |
| 21 – 192.1 – 1560.61 | 32 – 193.2 – 1551.72 | 43 – 194.3 – 1542.94 | 54 – 195.4 – 1534.18 |
| 22 – 192.2 – 1559.79 | 33 – 193.3 – 1550.92 | 44 – 194.4 – 1542.14 | 55 – 195.5 – 1533.40 |
| 23 – 192.3 – 1558.98 | 34 – 193.4 – 1550.12 | 45 – 194.5 – 1541.35 | 56 – 195.6 – 1532.63 |
| 24 – 192.4 – 1558.17 | 35 – 193.5 – 1549.32 | 46 – 194.6 – 1540.56 | 57 – 195.7 – 1531.85 |
| 25 – 192.5 – 1557.36 | 36 – 193.6 – 1548.52 | 47 – 194.7 – 1539.77 | 58 – 195.8 – 1531.08 |
| 26 – 192.6 – 1556.55 | 37 – 193.7 – 1547.72 | 48 – 194.8 – 1538.99 | 59 – 195.9 – 1530.31 |
| 27 – 192.7 – 1555.75 | 38 – 193.8 – 1546.92 | 49 – 194.9 – 1538.20 | 60 – 196.0 – 1529.54 |
| 28 – 192.8 – 1554.94 | 39 – 193.9 – 1546.12 | 50 – 195.0 – 1537.42 | 61 – 196.1 – 1528.77 |
| 29 – 192.9 – 1554.13 | 40 – 194.0 – 1545.32 | 51 – 195.1 – 1536.64 | |
| 30 – 193.0 – 1553.33 | 41 – 194.1 – 1544.53 | 52 – 195.2 – 1535.80 |
O-band DWDM refers to dense wavelength-division multiplexing operated in the O-band, the fibre-optic window around 1260–1360 nm.
Unlike the more common C-band systems, O-band transmission takes advantage of the fibre’s zero-dispersion region, which reduces chromatic dispersion and can simplify system design. O-band DWDM places many tightly spaced wavelengths in this window, enabling high-capacity links—especially for short-reach data-centre interconnects and emerging 800G/1.6T architectures where low latency and low dispersion are desirable.
O-band DWDM Frequency Table (150 GHz Grid)
| Part Number | Frequency (THz) | Wavelength (nm) |
|---|---|---|
| GQS-SIOA101-LR1C | 233.60 | 1283.36 |
| GQS-SIOB101-LR1C | 233.45 | 1284.18 |
| GQS-SIOC101-LR1C | 233.30 | 1285.01 |
| GQS-SIOD101-LR1C | 233.15 | 1285.84 |
| GQS-SIOE101-LR1C | 233.00 | 1286.66 |
| GQS-SIOF101-LR1C | 232.85 | 1287.49 |
| GQS-SIOG101-LR1C | 232.70 | 1288.32 |
| GQS-SIOH101-LR1C | 232.55 | 1289.15 |
| GQS-SIOI101-LR1C | 232.25 | 1290.82 |
| GQS-SIOJ101-LR1C | 232.10 | 1291.65 |
| GQS-SIOK101-LR1C | 231.95 | 1292.49 |
| GQS-SIOL101-LR1C | 231.80 | 1293.32 |
| GQS-SIOM101-LR1C | 231.65 | 1294.16 |
| GQS-SION101-LR1C | 231.50 | 1295.00 |
| GQS-SIOO101-LR1C | 231.35 | 1295.84 |
| GQS-SIOP101-LR1C | 231.20 | 1296.68 |
Gigalight 100G O band DWDM transceiver datasheet
Coherent Optics operating in the C Band
We have mentioned the problem of chromatic dispersion, which is the spreading in time of a pulse, which can lead to overlapping pulses which cannot be recovered by the receiver. effectively closing the eye pattern. Using Coherent Optics with intelligent DSP compensation can overcome this issue to some extent.
Coherent optics is an optical-communication technique in which both the amplitude and the phase of light are used to carry information. Instead of detecting only light intensity, on or off with a NRZ scheme or two levels with PAM4. Coherent receivers mix the incoming signal with a stable local oscillator locked laser. This allows them to precisely measure phase, frequency, and polarization.
By —Dipl-Ingo (Diskussion) 09:34, 4. Jan. 2013 (CET) – Link
Because of this extra information, coherent optics enables:
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Much higher data rates (100G, 400G, 800G, and beyond)
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Longer transmission distances thanks to better sensitivity
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Advanced modulation formats (QPSK, QAM)
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Digital signal processing to correct impairments like dispersion
400G BIDI CFP2-DCO Coherent Optical Module
Optical Amplification with Erbium-Doped Fibre Amplifiers (EDFAs)
The Gigalight CFP-2 400Ghz transceiver has an optical power budget of approximately 6dB which very roughly equates to a reach of 12-15km. In order to achieve more range an optical amplifier is required, and the Gigalight EDFA module is perfectly matched to work together with the transceiver. Gain is adjustable between 0 and 15dB extending the possible range to approximately 42km.
Gigalight Optical Amplifier (EDFA)
400G Muxponder Card
The Gigalight 400G Muxponder card accepts 4 x 100G standard optics and maps the connections to the CFP2 transceiver.
Network Monitoring Unit NMU
The Network Management Unit (G-1200D-1U-QNMU) introduced by Gigalight Communication is responsible for providing the interface between the system and the network management system, cooperating with the network management system to manage the various single cards of the equipment, and realizing the mutual communication among the equipment to complete the processing of the corresponding overhead and optical monitoring channels.
Conclusion
High bandwidth, long distance, affordable data centre connectivity for remote production is now possible, with several options to consider during implementation. DWDM multiplexing offers a large number of channels over a single fibre, which enables topologies with multiple flows between sites to be realised. Coherent optics can overcome some of the technical limitations of C band and O band non-linear optics, and can provide high speed link (400Gbps) tuneable over multiple DWDM channels. DCI systems available from Gigalight provides an integrated environment for coherent optics, including multiplexors, muxponders, amplifiers and control / monitoring cards.
