What is the difference between 1+1 Protection and 1:1 Protection?

We always hear that 1+1 protection or 1:1 protection in service transmit, especially in Huawei SDH and DWDM transmission fields, and there are special protection boards such as Huawei OSN8800 protection board DCP, OLP. What is the difference between 1+1 Protection and 1:1 Protection, this article will introduce you about that.

1+1 Protection

Each working channel has a dedicated protection channel.
At the transmit end, services are transmitted to both the working and protection channels. In normal cases, the receive end receives services from the working channel.

If the working channel becomes abnormal, the receive end selectively receives services from the protection channel based on channel status and external commands.

1:1 Protection

Each working channel corresponds to a protection channel, and they protect each other.
Services, however, are not concurrently transmitted to both the working and protection channels. Instead, the transmit end sends primary services to the working channel and extra services (low-level services) to the protection channel. Then, the receive end receives primary services from the working channel and extra services from the protection channel.

When the working channel is faulty, the transmit end sends primary services to the protection channel and the receive end receives primary services from the protection channel. At this time, the extra services are terminated to ensure normal transmission of the primary services.

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