10. A method comprising: receiving, from an optical receiver and by a device, a word, of a block of words within traffic, on which to perform forward error correction, the word including encoded bits and sets of reliability bits for identifying a respective level of reliability of each of the encoded bits; updating, by the device, a first segment of the word and a second segment of the word based on first extrinsic information, the first segment including a first subset of the encoded bits, the second segment including a second subset of the encoded bits, and the first extrinsic information modifying reliability bits associated with the first subset and the second subset; identifying, by the device, first least reliable positions (LRPs) within the updated first segment and second LRPs within the updated second segment, the first LRPs corresponding to first bits within the first subset with a lowest level of reliability, the second LRPs corresponding to second bits within the second subset with another lowest level of reliability; identifying, by the device, LRPs, within the word, based on a subset of a combination of the first bits and the second bits associated with one or more lowest levels of reliability; generating, by the device, candidate words based on different combinations of inverted encoded bits, within the word, that corresponds to the identified LRPs; identifying, by the device, errors within the word or the candidate words; updating, by the device and based on the first extrinsic information, a first encoded bit, within the first segment, in which an error is identified; determining, by the device, first partial distances between the updated first segment and first segments of the candidate words and second partial distances between the second segment and second segments of the candidate words; generating, by the device, second extrinsic information based on two or more best words of the candidate words, the two or more best words corresponding to two or more shortest first partial distances and two or more shortest second partial distances; and processing, by the device, a next word, of the block of words, using the second extrinsic information.
10. A method comprising: receiving, from an optical receiver and by a device, a word, of a block of words within traffic, on which to perform forward error correction, the word including encoded bits and sets of reliability bits for identifying a respective level of reliability of each of the encoded bits; updating, by the device, a first segment of the word and a second segment of the word based on first extrinsic information, the first segment including a first subset of the encoded bits, the second segment including a second subset of the encoded bits, and the first extrinsic information modifying reliability bits associated with the first subset and the second subset; identifying, by the device, first least reliable positions (LRPs) within the updated first segment and second LRPs within the updated second segment, the first LRPs corresponding to first bits within the first subset with a lowest level of reliability, the second LRPs corresponding to second bits within the second subset with another lowest level of reliability; identifying, by the device, LRPs, within the word, based on a subset of a combination of the first bits and the second bits associated with one or more lowest levels of reliability; generating, by the device, candidate words based on different combinations of inverted encoded bits, within the word, that corresponds to the identified LRPs; identifying, by the device, errors within the word or the candidate words; updating, by the device and based on the first extrinsic information, a first encoded bit, within the first segment, in which an error is identified; determining, by the device, first partial distances between the updated first segment and first segments of the candidate words and second partial distances between the second segment and second segments of the candidate words; generating, by the device, second extrinsic information based on two or more best words of the candidate words, the two or more best words corresponding to two or more shortest first partial distances and two or more shortest second partial distances; and processing, by the device, a next word, of the block of words, using the second extrinsic information. 16. The method of claim 10 , where the two or more best words include at least a best candidate word and a second best candidate word, the best candidate word being associated with a shortest distance that is less than: a distance between the second best candidate word and the encoded word, and other distances between other candidate words and the encoded word, and the second best candidate word being associated with a next shortest distance, the next shortest distance being less than the other distances.