What is the Difference Between 100G-BIDI and 100G-SR1.2

The 400G-BIDI Module from Arista is Capable of being Broken out into 4x 100G-BIDI or 4x 100G-SR1.2 Links. What is the Difference Between 100G-BIDI and 100G-SR1.2?

The difference between 100G-BIDI and 100G-SR1.2 is mainly in the number of optical lanes and the modulation solution. 100G-BIDI uses two optical lanes, one for each direction, over a duplex LC multi-mode fiber. 100G-SR1.2 uses four optical lanes, two for each direction, over the same fiber. 100G-BIDI uses NRZ (Non-Return-to-Zero) modulation, which means each bit is encoded as a single symbol. 100G-SR1.2 uses PAM4 (Pulse Amplitude Modulation) modulation, which means each symbol encodes two bits. PAM4 enables higher data rates with lower baud rates, but also introduces more noise and complexity. Both 100G-BIDI and 100G-SR1.2 are compliant to IEEE802.3bm 100GBASE-SR4 standard. The main advantage of 100G-BIDI is that it can reuse the existing 40G-BIDI infrastructure and reduce the fiber cabling cost. The main advantage of 100G-SR1.2 is that it can interoperate with 400G-SR4.2 and provide a future-proof solution for higher bandwidth demand.

Another difference between 100G-BIDI (100G-SRBD) and 100G-SR1.2 is the FEC (Forward Error Correction) used. 100G-BIDI (100G-SRBD) modules have been widely deployed for 100G operation over duplex MMF and use a FEC implementation that was developed prior to the IEEE standardization of KP-FEC for 50G PAM-4 based modules. Because of the differences in FEC implementation, 100G-SRBD and 100G-SR1.2 modules are not interoperable with each other.

FAQS

Q: 400G QSFP-DD vs 400G OSFP/CFP8: What are the differences?

A: The table below includes detailed comparisons for the three main form factors of 400G transceivers.

Q: How does the QSFP+ to SFP+ fiber convertor allow 4x 10G?

A: To enable 4x 10G connectivity, a QSFP+ to SFP+ fiber converter utilizes a breakout cable. This cable splits the 40G channel provided by the QSFP+ transceiver into four individual 10G channels, each connected to an SFP+ transceiver. Essentially, the converter breaks down the high-speed 40G signal into four separate 10G signals, allowing each SFP+ port to transmit data at 10G speeds. This configuration is beneficial for scenarios where equipment with SFP+ interfaces needs to communicate with a device equipped with a QSFP+ port, providing flexibility and compatibility in networking setups.

Q: What does “SR8”, “DR4”, “XDR4”, “FR4”, and “LR4” mean?

A: “SR” refers to short range, and “8” implies there are 8 optical channels. “DR” refers to 500m reach using single-mode fiber, and “4” implies there are 4 optical channels. “XDR4” is short for “eXtended reach DR4”. And “LR” refers to 10km reach using single-mode fiber.

Q: Can I plug an OSFP transceiver module into a QSFP-DD port?

A: No. QSFP-DD and OSFP are totally different form factors. For more information about QSFP-DD transceivers, you can refer to 400G QSFP-DD Transceiver Types Overview. You can use only one kind of form factor in the corresponding system. E.g., if you have an OSFP system, OSFP transceivers and cables must be used.

Q: What other breakout options are possible apart from using OSFP modules mentioned above?

A: OSFP 400G DACs & AOCs are possible for breakout 400G connections. See 400G Direct Attach Cables (DAC & AOC) Overview for more information about 400G DACs & AOCs.

Q1: What is the difference between QSFP28 ER4 and QSFP28 ER4 Lite Module?

A: The QSFP 100G ER4 has a series of BER requirements of better than 1E-12 without FEC optical modules. However, the receiving sensitivity of 100G QSFP28 ER4 is not satisfied with the existing APD technology. Therefore, many optical module manufacturers/suppliers defined a non-standard 100Gbase ER4 Lite module with a QSFP28 package where the largest transmission distance is up to 40km with FEC or 30km without FEC.?Walsun provides the QSFP28 100G ER4 Lite module compliant with the Ethernet 100Gbase ER4 Lite standard to meet the harshest external operating conditions including temperature, humidity, and EMI interference.

Q2: How does the QSFP 100G ER4 Module differ from the QSFP28 4WDM?

A: The QSFP 100G ER4 optical transceiver supports dual 100G Ethernet applications while the 100G QSFP28 4DWM only supports 100G Ethernet applications. The commons and differences are listed below.