There are various form-factors available above 10G, such as the QSFP (Quad Small Form-factor Pluggable) for 40G and QSFP28 for 100G and CFP.  The ‘C Form-factor Pluggable’ is seen in three different shapes; CFP, CFP2, and CFP4.  Over time the size of the CFP was reduced twice by a scale factor of two, which resulted in the CFP4. The latest form-factor available in the market is the QSFP-DD. 

Optical Transceivers have different specifications for different needs; They can differ in speed from 100mbit to 400G. They can also differ in strength measured in dB power budget from 10dB to 41dB. And  they are also available in different light colors used in the multiplexing techniques like CWDM and DWDM.  Most Router and Switch hardware producers focus on just a fraction of what is available on the optical transceiver market. Solid Optics can provide you with a wide variety of compatible transceiver options for close to 100 brands such as Cisco, Juniper, HP, Dell, Brocade, Arista, Alcatel-Lucent and many more.