The QSFP-40G-SR-BD transceiver is designed for use with a specific type of multimode fiber optic cable known as "BiDi" or "Bidirectional" fiber. The "BD" in the transceiver's name stands for Bidirectional.

Here are some key characteristics of QSFP-40G-SR-BD:

1. Data Rate: QSFP-40G-SR-BD supports a data rate of 40 gigabits per second (Gbps).

2. Wavelengths: Bidirectional (BiDi) optics operate over a single pair of fibers, using two different wavelengths for transmitting and receiving. QSFP-40G-SR-BD typically uses a wavelength division multiplexing (WDM) technology with two different wavelengths on a single fiber pair.

3. Fiber Type: QSFP-40G-SR-BD is designed for use with duplex multimode fiber (MMF). The use of bidirectional optics allows for bidirectional communication over a single pair of fibers.

4. Distance: The achievable distance with QSFP-40G-SR-BD depends on factors such as the quality of the fiber, modal bandwidth, and the specific implementation. It is generally suitable for short-distance connections within data centers, often reaching distances up to 150 meters.

When deploying QSFP-40G-SR-BD transceivers, it is important to use the appropriate multimode fiber optic cables that support bidirectional transmission. Always refer to the specifications and compatibility guidelines provided by the transceiver's manufacturer to ensure proper functionality and performance in your network environment.