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Gigalight's 12G-SDI Video over Fiber Solution

Number of visits: Date:2018-6-19 16:20


Overview of 12G-SDI Standard and the Market’s Background

As the picture of broadcast-quality imaging machines on the market has become more and more popular in 4K high-definition displays, suppliers of professional video such as broadcasting will continue to upgrade their existing digital transmission interfaces to support higher-resolution video and meet growing demand of digital video bandwidth.

Prior to this, for the 4K uncompressed digital baseband signals, the market adopted 4-channel parallel transmission (operating rate up to 3Gb/s per channel), but this will bring two obvious problems in practical applications. The first problem is that 4 panels with BNC connectors are needed, which will take up too much valuable equipment space. The second problem is the cabling challenge, which requires 4 copper-axis cables to connect and consume too much cable resources.

In order to deal with these problems, in 2015, the SMPTE (Society of Motion Picture and Television Engineers) standard organization released the uncompressed digital baseband 12G-SDI interface standard (Table 1) for 4K UHD (2160p60) image quality. At 12Gb/s, only a BNC connector and a high-speed cable are required to transmit 4K ultra-high-definition signals, saving valuable equipment space and cable resources (see Figure 1).

Standard Released Time Data Rate Video Format
SMPTE 424M 2006 2.97Gb/s 1080p60
SMPTE ST 2081 2015 5.94Gb/s 2160p30
SMPTE ST 2082 2015 11.88Gb/s 2160p60

Table 1. 12G-SDI Interface Standard

4-channel 3G-SDI and Single-channel 12G-SDI

4-channel 3G-SDI and Single-channel 12G-SDI

Difficulty of the 12G-SDI Video over Cooper Cable: Distance is Limited

On the equipment side, the 12G-SDI high-speed baseband signal is pre-emphasized and equalized, and the transmission distance on the copper-axis cable can reach 70 meters. The following table (Table 2) is a typical transmission distance reference for 75Ω copper cable provided by professional video equipment manufacturers. From the table we can see that the higher the operating speed is, the shorter the transmission distance over copper-axis cable is. In some special applications, such as large events and huge studio environments, the copper transmission distance is limited by physical limits. Copper-axis cables cannot meet the long-distance transmission requirements of professional users for 12G-SDI signal baseband. At this time, we can solve this problem with optical fiber transmission extension solutions.

Standard Data Rate Distance @Copper-axis (75Ω) Pre-emphasis and Equalization
12G-SDI 11.88Gb/s 70m Yes
6G-SDI 5.94Gb/s 120m Yes
3G-SDI 2.97Gb/s 190m Yes

Table 2. Typical Transmission Distance Reference for 75Ω Copper-axis Cable

Gigalight's 12G-SDI Video over Fiber Solution

Gigalight has developed 12G-SDI optical modules and 12G-SDI optical extenders to cope with the long-distance transmission of 12G-SDI baseband signals. Gigalight's CWDM Mux/DeMux can be used on a single-mode fiber, multi-channel 12G-SDI high-speed signal transmission can be guaranteed under the condition of complete 12G-SDI ill-conditioned frames, and the transmission distance can reach 20km under 12G-SDI Color bar. Unlike transmission of 12G-SDI copper-axis cable, 12G-SDI optical transmission must solve the stress test under 12G-SDI pathological signal test conditions, which is very important for the performance of the transmission system.

Gigalight’s 12G-SDI Video over Fiber Solution

Figure 2. Typical CWDM Scheme Schematic (10km to 20km Solution)

Introduction of 12G-SDI Pathological Signal Test

The 12G-SDI pathological signal test is a special stress test. The test pattern contains a large amount of low-frequency energy. Its original intention is to test the robustness of the entire transmission system and to consider whether the system can transmit 12G-SDI baseband signals under the worst conditions of the transmission signal. Gigalight uses a professional 12G-SDI video tester (PHABRIX) to output and test 12G-SDI disease codes, including a total of eight 100% Bar patterns. Gigalight's 12G-SDI optical modules and 12G-SDI optical extenders can pass the test of these patterns completely.

12G-SDI Pathological Signal Test

Figure 3. 12G-SDI Pathological Signal Test


Gigalight's 12G-SDI optical modules and 12G-SDI optical extenders are fully compliant with SMPTE ST-297-2015, ST 2081 and ST 2082 standards, and are perfectly backward-compatible with 6G-SDI, 3G-SDI, HD-SDI, and SD-SDI data rates. While meeting the demand of 12G-SDI pathological signal test, they provide affordable 4K super video for the broadcast video industry under tight or scarce fiber resources HD ultra-long distance fiber transmission solution with Gigalight CWDM Mux/DeMux.

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